Polymetalosilazane, process of producing same, silicon nitride based ceramic, and process of preparing same

A preceramic polymetalosilazane substantially free of Si-O groups is produced by reacting a polysilazane with a metal alkoxide in the presence of an alkylsilazane or alkylsilane. The preceramic polymer gives a high strength and heat resistant ceramic body which remains amorphous when calcined at 1,600.degree. C. for 10 hours in the atmosphere of nitrogen.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a low oxygen content polymetalosilazane and to a 
process of producing same.: The present invention also pertains to a 
metal-containing silicon nitride ceramic and to a process of preparing 
same. 
2. The Prior Art 
Ceramic fibers have been attracting much attention for their favorable 
properties such as high mechanical strengths and resistance to heat and 
chemicals and will find use for a variety of applications as reinforcing 
materials for various composite articles such as engine parts, fan blades 
and aircraft structures. 
U.S. Pat. No. 4,886,860 discloses a process of preparing a 
polymetalosilazane wherein a polysilazane having a number molecular weight 
of 100-50,000 and having a skeleton consisting essentially of units of the 
following general formula: 
##STR1## 
wherein R.sup.1, R.sup.2 and R.sup.3 is independently selected from 
hydrogen, an alkyl group, an alkenyl group, a cycloalkyl group, an aryl 
group, a group other than the above-mentioned groups in which the atom 
bonded directly to the silicon atom is a carbon atom, an alkylsilyl group, 
an alkylamino group and an alkoxy group is reacted with a metal alkoxide 
of the formula: 
EQU M(OR.sup.4).sub.n 
wherein M is a metal selected from those of groups IIA and III through V of 
the Periodic Table, R.sub.4 is hydrogen, an alkyl having 1-20 carbon atoms 
or an aryl and n is the valence of the metal M with the proviso that at 
least one of the R.sub.4 groups is the alkyl group or aryl group. The 
polymetalosilazane obtained by the above method unavoidably contains 
oxygen derived from the metal alkoxide. The oxygen introduced into the 
polymer is converted into SiO gas during the calcining stage so that small 
pores or gaps are apt to be formed in the ceramic product, which adversely 
affects the mechanical strengths and heat resistance of the ceramic. 
U.S. Pat. No. 4,730,026 (equivalent of EP-A-262,914) discloses a 
polymetalosilazane which is obtained by reacting a silazane with an 
oxygen-free metal compound such as an alkyl metal or a metal halide and in 
which the silazane is cross-linked with, for example, --MR-- linkages. a 
ceramic body obtained therefrom. The polymetalosilazane obtained using the 
oxygen free metal compound gives a ceramic having a low oxygen content. 
However, the above method is not practical and requires much costs because 
the metal compound is dangerous. 
SUMMARY OF THE INVENTION 
In accordance with one aspect of the present invention, there is provided a 
silicon nitride ceramic containing Si, N, at least one metal M which is 
selected from those of the groups IIa, IIIa, IIIb, IVa IVb, Va and Vb of 
the Periodic Table, 0 and C in amounts providing the following atomic 
ratios: 
N/Si : 0.05 to 3, 
M/Si : 0.05 to 3, 
O/M : 1 or less, and 
C/Si : 1 or less 
said ceramic being amorphous when calcined at 1,600.degree. C. for 10 hours 
in the atmosphere of an inert gas and having a three-point bending 
strength of at least 2 MPa. 
In another aspect, the present invention provides a silicon nitride ceramic 
fiber containing Si, N, at least one metal M which is selected from those 
of the groups IIa, IIIa, IIIb, IVa IVb, Va and Vb of the Periodic Table, 0 
and C in amounts providing the following atomic ratios: 
N/Si : 0.05 to 3, 
M/Si : 0.05 to 3, 
O/M : 1 or less, and 
C/Si : 1 or less 
said ceramic fiber being amorphous when calcined at 1,500.degree. C. for 1 
hour in the atmosphere of an inert gas and having a tensile strength of at 
least 100 kg/mm.sup.2. 
In a further aspect, the present invention provides a process of producing 
a silicon nitride ceramic, comprising the steps of: 
reacting a polysilazane with a metal alkoxide of the formula: 
EQU M(OR.sup.3).sub.n 
wherein M is as defined above, R.sub.3 is hydrogen, an alkyl group having 
1-20 carbon atoms or an aryl group and n is the valence of the metal M 
with the proviso that at least one of the n number of the R.sub.3 is the 
alkyl group or aryl group, in the presence of a silicon compound 
represented by the following general formula: 
##STR2## 
wherein R.sup.4, R.sup.5, R.sup.6 and R.sup.7, independently from each 
other, represent hydrogen, a hydrocarbyl group, a substituted hydrocarbyl 
group, an alkylsilyl group, an alkylamino group, an alkoxy group, 
--SR.sup.8 where R.sup.8 represents hydrogen or an alkyl group or 
--SR.sup.9 R.sup.10 R.sup.11 where R.sup.9, R.sup.10 and R.sup.11, 
independently from each other, represent hydrogen or an alkyl group, to 
obtain a polymetalosilazane; and 
calcining said polymetalosilazane at a temperature of 
400.degree.-1,800.degree. C. 
The present invention also provides a process of producing a 
polymetalosilazane, comprising reacting a polysilazane with a metal 
alkoxide of the formula: 
EQU M(OR.sup.3).sub.n 
wherein M is as defined above, R.sub.3 is hydrogen, an alkyl group having 
1-20 carbon atoms or an aryl group and n is the valence of the metal M 
with the proviso that at least one of the n number of the R.sub.3 is the 
alkyl group or aryl group, in the presence of a silicon compound 
represented by the following general formula: 
##STR3## 
wherein R.sup.4, R.sup.5, R.sup.6 and R.sup.7, independently from each 
other, represent hydrogen, a hydrocarbyl group, a substituted hydrocarbyl 
group, an alkylsilyl group, an alkylamino group, an alkoxy group, 
--SR.sup.8 where R.sup.8 represents hydrogen or an alkyl group or 
--SR.sup.9 R.sup.10 R.sup.11 where R.sup.9, R.sup.10 and R.sup.11, 
independently from each other, represent hydrogen or an alkyl group. 
In a further aspect, the present invention provides a polymetalosilazane 
obtained by the above method.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention will now be described in detail below. 
The ceramic according to the present invention contains Si, N and at least 
one metal M. It is important that the amount of Si, N and M should be such 
as to provide the following atomic ratios: 
N/Si : 0.05 to 3, 
M/Si : 0.05 to 3, 
O/M : 1 or less, and 
C/Si : 1 or less 
A proportion of the metal M below the above specified range causes 
reduction of the mechanical strengths and heat resistance of the ceramics. 
Too large an amount of the metal M in excess of the above specified range 
is disadvantage because the substance is no longer a ceramic. Preferred 
atomic ratios are as follows: 
N/Si : 0.05 to 2 
M/Si : 0.05 to 1 
O/M : 0.5 or less 
C/Si : 0.2 or less 
The metal M is preferably at least one element selected from those of the 
groups IIa, IIIa, IIIb, IVa IVb, Va and Vb of the Periodic Table. 
Illustrative of suitable metals are Be, Mg, Ca, Sr, Ba, Sc, Y, lanthanoid 
elements, actinoid elements, B, A1, Ga, In, T1, Ti, Zr, Hf, Ge, Sn, Pb, V, 
Nb, Ta, As, Sb, and Bi. Above all, Y, B, A1, Ti and Zr are especially 
preferred. 
The ceramic according to the present invention is characterized by high 
mechanical strengths and high heat resistance. For example, when the 
ceramic is in the form of a plate, the three-point bending strength 
thereof is at least 2 MPa. In the form of a fiber, the tensile strength is 
at least 100 kgf/mm.sup.2. The shaped ceramic bodies retains their 
amorphous state and high mechanical strength even after being subjected to 
a high temperature. For example, a ceramic plate according to the present 
invention remains amorphous even when heated at 1,600.degree. C. for 10 
hours in the atmosphere of an inert gas and a ceramic fiber of the present 
invention remains amorphous when heated at 1,500.degree. C. for 1 hour. 
These characteristics of the ceramic bodies according to the present 
invention are considered to be attributed to the presence of the metal and 
to the low oxygen and carbon contents. The presence of the metal in the 
ceramic serves to prevent the formation of crystals so that the ceramic 
remains amorphous even when subjected to such a high temperature as to be 
favorable for the formation of crystals. The formation of crystals in the 
amorphous ceramic bodies adversely affect the mechanical strengths and 
heat resistance thereof. The fact that the ceramic has low oxygen and 
carbon contents means that the preceramic polymer from which the ceramic 
has been prepared, too, has low oxygen and carbon contents. Since the 
oxygen and carbon contained in the preceramic polymer are converted into 
SiO, CO and CO.sub.2 gases when heated at a temperature of 1,200.degree. 
C., fine pores or gaps are apt to be formed in the ceramic body obtained 
by calcination thereof. 
The process for the production of the ceramic according to the present 
invention will now be described below. 
PREATION OF PRECERAMIC POLYMETALOSILAZANE 
The polymetalosilazane is produced by reacting a polysilazane with a metal 
alkoxide of the formula (II): 
EQU M(OR.sup.3).sub.n (II) 
wherein M is as defined above, R.sub.3 is hydrogen, an alkyl group having 
1-20 carbon atoms or an aryl group and n is the valence of the metal M 
with the proviso that at least one of the n number of the R.sub.3 is the 
alkyl group or aryl group, in the presence of a silicon compound 
represented by the following general formula (III): 
##STR4## 
wherein R.sup.4, R.sup.5, R.sup.6 and R.sup.7, independently from each 
other, represent hydrogen, a hydrocarbyl group, a substituted hydrocarbyl 
group, an alkylsilyl group, an alkylamino group, an alkoxy group, 
--SR.sup.8 where R.sup.8 represents hydrogen or an alkyl group or 
--SR.sup.9 R.sup.10 R.sup.11 where R.sup.9, R.sup.10 and R.sup.11, 
independently from each other, represent hydrogen or an alkyl group. 
The polysilazane preferably has a number average molecular weight of 
100-500,000 and a main skeletal .structure containing the following 
recurring unit (I): 
##STR5## 
wherein R.sup.1 and R.sup.2, independently from each other, represent 
hydrogen, a hydrocarbyl group, a substituted hydrocarbyl group, an 
alkylsilyl group, an alkylamino group or an alkoxy group, 
Preferably the hydrocarbyl group of R.sup.1, R.sup.2, R.sup.4, R.sup.5, 
R.sup.6 and R.sup.7 is an alkyl, alkenyl, an aryl, a cycloalkyl or 
aralkyl. 
Examples of suitable substituents R.sup.1 and R.sup.2 of the polysilazane 
of the formula (I) include hydrogen, an alkyl group having 1-5 carbon 
atoms, an alkenyl group having 2-6 carbon atoms, a cycloalkyl group having 
5-7 carbon atoms, an aryl group, an alkylsilyl group having 1-4 carbon 
atoms, an alkyl amino group having 1-5 carbon atoms and an alkoxy group 
having 1-5 carbon atoms. Above all, hydrogen, a methyl group, an ethyl 
group, a vinyl group, a methylamino group, an ethylamino group, a methoxy 
group and an ethoxy group. 
Examples of suitable substituent R.sup.3 of the metal alkoxide of the 
formula (II) include hydrogen, a methyl. group, a n-propyl group, an 
i-propyl group, a n-butyl group, an i-butyl group, a t-butyl group, a 
phenyl group, a benzyl 4 group and a tolyl group. The amount of the metal 
alkoxide relative to the polysilazane is preferably such as to provide an 
atomic ratio M/Si of 0.001-60, more preferably 0.01-5, most preferably 
0.05-2.5. Too small an amount of the metal alkoxide below M/Si of 0.001 is 
insufficient to obtain highly cross-linked polymetalosilazane, while too 
large an amount of the metal alkoxide in excess of M/Si of 60 gives no 
additional merit and is economically disadvantageous. 
Examples of suitable silicon compound of the formula (III) include alkyl 
silazanes such as trimethylsilylamine ((CH.sub.3).sub.3 SiNH.sub.2) 
trimethyldimethylsilylamine ((CH.sub.3).sub.3 SiN(CH.sub.3).sub.2) and 
dimethylsilylamine ((CH.sub.3).sub.2 SiHNH.sub.2); alkyldisilazanes such 
as hexamethyldisilazane ((CH.sub.3).sub.3 SiNHSi(CH.sub.3).sub.3), 
heptamethyldisilazane ((CH.sub.3).sub.3 SiNCH.sub.3 Si(CH.sub.3).sub.3) 
and tetramethyldisilazane ((CH.sub.3).sub.2 SiHNHSiH(CH.sub.3).sub.2); 
alkylhalosilanes such as trimethylchlorosilane ((CH.sub.3).sub.3 SiCl), 
dichlorosilane (SiH.sub.2 Cl.sub.2), dimethyldichlorosilane 
((CH.sub.3).sub.2 SiCl.sub.2), monomethylchlorosilane 
((CH.sub.3)SiHCl.sub.2), trimethylbromosilane ((CH.sub.3).sub.3 SiBr) and 
trimethyliodosilane ((CH.sub.3).sub.3 SiI); alkylsilanes; and 
alkyldisilanes such as hexamethyldisilane ((CH.sub.3).sub.3 
SiSi(CH.sub.3).sub.3) and tetramethyldisilane ((CH.sub.3).sub.2 
SiHSiH(CH.sub.3).sub.2). The alkyl groups of the silicon compounds are 
suitably lower alkyl groups such as a methyl group. The silicon compound 
(III) is preferably used in an amount of at least 1 mole per mole of the 
polysilazane (I), more preferably in an amount of at least n (which equals 
the valence of the metal M of the metal alkoxide) moles per mole of the 
metal alkoxide (II). 
The reaction for the formation of the polymetalosilazane is preferably 
performed using an inert solvent such as an aromatic hydrocarbon, an 
aliphatic hydrocarbon, an alicyclic hydrocarbon, a halogenated 
hydrocarbon, an aliphatic ether or an alicyclic ether. Illustrative of 
suitable solvents are benzene, toluene, xylene, methylene chloride, 
chloroform, n-hexane, ethyl ether and tetrahydrofuran. The reaction is 
preferably performed at a temperature of not higher than 400.degree. C. 
for reasons of preventing the formation of a gel by the decomposition of 
the polymetalosilazane. For the purpose of obtaining a polymetalosilazane 
with a high number average molecular weight, it is advisable to perform 
the reaction below the boiling point of the solvent and then complete the 
reaction at a temperature higher than the boiling point of the solvent 
while removing the solvent by evaporation. 
The reaction is generally performed at ambient pressure for 30 minutes to 
24 hours. A reaction time longer than 24 hours can increase the molecular 
weight of the polymetalosilazane. For preventing the oxidation and/or 
hydrolysis of the starting materials, it is preferred that the reaction be 
performed in the atmosphere of an inert gas such as nitrogen or argon. The 
unreacted metal alkoxide can be separated from the polymetalosilazane 
product by vacuum distillation or liquid chromatography. 
By reaction of the polysilazane with the metal alkoxide, an alcohol is 
produced together with the polymetalosilazane as follows: 
##STR6## 
The thus produced alcohol R3OH readily reacts with the raw material 
polysilazane or the polymetalosilazane to cleave the skeletal chain 
thereof with the simultaneous introduction of alkoxide groups --OR.sup.3 
into the cleaved cites, for example, as follows: 
##STR7## 
When the silicon compound of the formula (III) is present, however, the 
alcohol is reacted with the silicon compound rather than with the 
polymetalosilazane or polysilazane: 
##STR8## 
Thus, the presence of the silicon compound of the formula (III) can 
effectively prevent the cleavage of the polysilazane and 
polymetalosilazane polymer chains and the introduction of the oxygen (as 
Si--O--R.sup.3) into the polymetalosilazane. 
The polymetalosilazane thus obtained by the process of the present 
invention is substantially free of Si-O bonds. Preferably, the 
polymetalosilazane has a number average molecular weight of 200-500,000, 
more preferably 400-300,000 and an M/Si atomic ratio of 0.001-3, more 
preferably 0.01-2.0. Since the polymetalosilazane is generally soluble in 
a solvent, it is easy to obtain a shaped ceramic body such as a plate, 
block, cylinder, pipe or fiber. Further, the polymetalosilazane does not 
need an infusiblization treatment such as oxidation, so that it is 
possible to obtain a ceramic product having a low oxygen content. 
PREATION OF SHAPED CERAMIC BODIES 
The preceramic polymetalosilazane is shaped into a desired form and 
calcined to obtain a shaped ceramic body. If desired, an additive such as 
a hardening agent or ceramic powder may be mixed with the preceramic 
polymer. Examples of suitable hardening agent include organic amines such 
as alkylamines and alkylene diamines; acid anhydrides such as oxalic 
anhydride and malonic anhydride; isocyanates such as alkylisocyanates and 
dimethylsilyldiisocyanate; thiols such as butane dithiol and benzene 
dithiol; imides such as malonimide and succinimide; metal alkoxides such 
as alkoxides of metals of groups IIa and III-V of the Periodic Table; and 
metal halides such as those of iron, cobalt, nickel, copper, silver, gold, 
mercury, zinc, ruthenium, paradium, indium, titanium, hafnium, zirconium, 
aluminum, boron and phosphorus. Examples of ceramic powder which is used 
for preventing cracks or increasing mechanical strengths include nitrides, 
carbides and oxides of metals. 
For example, the preceramic polymer is dissolved in a suitable solvent such 
as a hydrocarbon, a halogenated hydrocarbon or an ether and the solution 
is filled in a mold cavity. The solution is then heated under atmospheric 
pressure or under a reduced pressure to remove the solvent, thereby to 
form a shaped body. Alternatively, the preceramic polymer in the form a 
solid is directly filled in a mold cavity and heated from room temperature 
to a temperature of 400.degree. C. at maximum at a pressure of up to 10 
atm. In the case of a liquid preceramic polymer, the polymer is directly 
filled in a mold cavity and heated from room temperature to a temperature 
of 400.degree. C. at maximum under a reduced pressure or at a pressure of 
up to 10 atm. The molding of the preceramic polymer may be performed in 
the atmosphere of an inert gas such as nitrogen or argon, a reducing gas 
such as ammonia, hydrogen, methylamine or hydrazine, an oxidizing gas such 
as air, oxygen or ozone, or a mixed gas thereof. Any known suitable mold 
may be used. Preferably, a mold releasing agent such as a silicone-based 
agent or a grease may be applied to the inside surface of the mold. 
The preceramic polymer according to the present invention may be shaped 
into fibers by spinning through a nozzle. Thus, the polymer is dissolved 
in a suitable solvent and the solution is concentrated in vacuo until a 
suitable viscosity is reached. The amount of the polymetalosilazane in the 
solution is not critical as long as the solution can exhibit a suitable 
spinnability. Generally, however, a concentration of 50-98% by weight 
gives good results. Optimum concentration varies with the number average 
molecular weight, molecular weight distribution and molecular structure of 
the polymetalosilazane. 
Before spinning, the spinning solution is desirably subjected to defoaming, 
filtration and other treatments for the removal of gels and foreign 
matters which will adversely affect the spinnability. The spinning is 
advantageously effected by a dry spinning method. Alternatively, 
centrifugal or blow spinning methods can be adopted. In dry spinning, the 
solution is discharged through a spinning nozzle to a cylinder and the 
spun fibers are continuously wound around a roll. The nozzle diameter, 
spinning speed and winding speed vary with the property of the spinning 
solution and with the intended diameter of the spun fibers. A nozzle 
diameter of 0.035-0.5 mm, preferably 0.05-0.3 mm and a winding speed of 
30-5000 m/minute, preferably 60-2500 m/minute are generally used. The 
inside of the cylinder into which the fibers are discharged from the 
spinning nozzle can be maintained in any desired atmosphere such as air. 
It is, however, preferable to maintain the inside of the cylinder in a 
dried air atmosphere, an ammoniacal atmosphere or an inert gas atmosphere 
for the purpose of controlling the infusiblization and solidification of 
the spun fibers. The spinning solution is generally maintained at a 
temperature of 10.degree.-300.degree. C. and the temperature within the 
cylinder is generally held at a temperature of 20.degree.-300.degree. C. 
The polymetalosilazane may also be shaped into a film by coating a solution 
thereof onto a surface of a metal or a ceramic and, then, drying the 
coating by evaporation of the solvent. 
The thus obtained shaped body of the polymetalosilazane is then pyrolyzed 
or calcined at temperatures of 400.degree.-1,800.degree. C. to form a 
ceramic body. The pyrolysis is preferably carried out in the atmosphere of 
an inert gas such as described above, a reducing gas such as described 
above or a mixture thereof, or under vacuum. Preferably a heating rate of 
20.degree. C./minute or less, more preferably 5.degree. C./minute or less, 
is used for the heating of the shaped body from 400.degree. C. to 
1,800.degree. C. When the maximum temperature, for example, 1,800.degree. 
C. is reached, the pyrolysis is further continued at that temperature for 
48 hours or less. If desired, pyrolysis is performed under pressure using 
a hot press. Further, the ceramic body obtained by the pyrolysis may be 
impregnated with a solution of the polymetalosilazane and calcined again. 
It is advisable to maintain the pyrolysis temperature not higher than 
1,800.degree. C. for avoiding the formation of crystals. 
The following examples will further illustrate the present invention. 
The elementary analysis was performed with ICP (inductive coupled plasma 
emission spectroscope) for the determination of Si and M, a 
nitrogen-oxygen simultaneous analyzer (EM6A-2800 manufactured by Horiba 
Inc.) for N and O and a carbon-hydrogen-nitrogen simultaneous analyzer 
(CHN Rapid Analyzer manufactured by Helaus Inc.). 
The crystalophase of ceramics was determined by the X-ray diffraction 
analysis. Before analysis, the sample was ground into particles having a 
particle size of in the range of 10-100 .mu.m and the ground powder was 
heated at 1,600.degree. C. for 10 hours in the atmosphere of nitrogen. 
The three-point bending strength was measured with a universal tester with 
a spun of 10 mm and a load applying speed of 1 mm/minute. The sample had a 
sectional area of 4-7 mm.sup.2. 
The tensile strength was measured with an autograph (AG-2000C manufactured 
by Shimadzu Seisakusho Ltd.) 
REFERENCE EXAMPLE 1 
Preparation of Perhydropolysilazane 
To a four-necked, 1 liter flask equipped with a gas feed conduit, a 
mechanical stirrer and a Dewar condenser, an oxygen-free, dry nitrogen gas 
was fed to replace the air within the flask therewith. After charging 490 
ml of deaerated, dry pyridine, the flask was cooled in an ice bath. Then, 
51.9 g of dichlorosilane was added into the flask to form a white, solid 
precipitate of an adduct (SiH.sub.2 Cl.sub.2 .multidot.2C.sub.5 H.sub.5 
N). Subsequently, with stirring and cooling the reaction mixture in the 
ice bath, 51.0 g of ammonia, which had been refined by being passed 
successively through a sodium hydroxide-containing tube and an active 
carbon-containing tube, was bubbled through the reaction mixture within 
the flask. The reaction mixture was then heated at 100.degree. C. for the 
completion of the reaction. 
Thereafter, the reaction mixture was centrifuged, and the supernatant was 
washed with dry pyridine, followed by filtration in a nitrogen atmosphere 
to give 850 ml of a filtrate containing perhydropolysilazane. When the 
solvent was removed from the liltrate (5 ml) by evaporation in vacuo, 
0.102 g of resinous solid, perhydropolysilazane was obtained. The analysis 
by the cryoscopic method revealed that the perhydropolysilazane had a 
number-average molecular weight of 1,120. The infrared spectrum of this 
polymer (solvent: dry o-xylene; concentration of the perhydropolysilazane: 
10.2 g/liter) is shown in FIG. 12. There are absorption peaks based on NH 
at wave numbers of 3,350 cm.sup.-1 (apparent absorptivity coefficient 
.epsilon.=0.557 1 g.sup.-1 cm.sup.-1) and 1,175 cm.sup.-1, a peak at 2,170 
cm.sup.-1 (.epsilon.=3.14) based on SiH, a broad peak at 1,020-820 
cm.sup.-1 based on Si-N-Si. The .sup.1 HNMR (proton nuclear magnetic 
resonance) spectrum of (60 MHz; solvent: CDCl.sub.3 ; reference substance: 
TMS) of this polymer indicated broad peaks at .delta. of 4.8, 4.4 (br, 
SiH) and 1.5 (br, NH), as shown in FIG. 13. 
REFERENCE EXAMPLE 2 
Production of Polymethyl(hydro)silazane: 
To a four-necked, 500 ml liter flask equipped with a gas feed conduit, a 
mechanical stirrer and a Dewar condenser, an oxygen-free, dry nitrogen gas 
was fed to replace the air within the flask therewith. After charging 300 
ml of dry dichloromethane and 24.3 g (0.221 mol) of methyldichlorosilane, 
the flask was cooled in an ice bath. Then, with stirring, 20.5 g (1.20 
mol) of dry ammonia was bubbled, together with nitrogen, through the 
reaction mixture within the flask. After completion of the reaction, the 
reaction mixture was centrifuged, followed by filtration. When the solvent 
was removed from the filtrate by evaporation in vacuo, 8.79 g of 
colorless, transparent methyl(hydro)silazane was obtained. The cryoscopic 
analysis revealed that the polymethyl(hydro)- silazane had a 
number-average molecular weight of 310. 
To a four-necked, 100 ml flask equipped with a gas feed conduit, a 
thermometer, a dropping funnel and a condenser, an argon gas was fed to 
replace the air within the flask therewith. Then, 12 ml of tetrahydrofuran 
and 0.189 g (4.71 mol) of potassium hydroxide were charged into the flask 
and stirred with a magnetic stirrer. The polymethyl(hydro)silazane (5.0 g) 
obtained above and 50 ml of dry 8 tetrahydrofuran were charged into the 
dropping funnel and 9 added dropwise to the mixture in the flask. The 
resulting mixture was reacted at room temperature for 1 hour. Thereafter, 
1.60 g (11.3 mmol) of methyl iodide and 1 ml of dry tetrahydrofuran were 
charged into the dropping funnel and added dropwise into the mixture in 
the flask. The resulting mixture was reacted at room temperature for 3 
hours. The solvent was then removed in vacuo from the reaction mixture and 
the residues were mixed with 40 ml of dry n-hexane. The mixture was 
centrifuged and filtered and the solvent was removed from the filtrate in 
vacuo to obtain 4.85 g of white powder of polymethyl(hydro)silazane. 
The polymethyl(hydro)silazane thus obtained was found to have a 
number-average molecular weight of 1,060. The infrared spectrum of this 
polymer (solvent: dry o-xylene; concentration of the 
polymethyl(hydro)silazane: 43.2 g/liter) is shown in FIG. 14. There are 
absorption peaks based on NH at wave numbers of 3,380 cm.sup.-1 (apparent 
absorptivity coefficient .epsilon.=0.249 1 g.sup.-1 cm.sup.-1) and 1160 
cm.sup.-1, a peak at 2,120 cm.sup.-1 (.epsilon.=0.822) based on SiH, a 
peak at 1,255 cm.sup.-1 based on Si-CH.sub.3. The .sup.1 HNMR (proton 
nuclear magnetic resonance) spectrum of (60 MHz; solvent: CDCl.sub.3 ; 
reference substance: TMS) of this polymer indicated peaks at .delta.4.7 
(Si-H, 0.56H), .delta.2.4 (N-CH.sub.3, 0.15H), .delta.0.7 (NH, 0.51H) and 
.delta.0.2 (Si-CH.sub.3), as shown in FIG. 15. Accordingly, the polymer 
was found to have a composition of (CH.sub.3 SiHNH).sub.0.51 (CH.sub.3 
SiN).sub.0.44 (CH.sub.3 SiHNCH.sub. 3).sub.0.05. 
COMATIVE EXAMPLE 1 
Production of Polyborosilazane 
To a 200 ml four-necked flask equipped with a gas feed conduit, a dropping 
funnel, a thermometer and a magnetic stirrer, a dry nitrogen gas was fed 
for replacing the air therewith. Then, 110 g of a solution of the 
perhydropolysilazane obtained in Reference Example 1 in benzene 
(concentration of perhydropolysilazane: 4.57% by weight) was charged into 
the flask. A solution of 2.90 g (27.9 mmol) of trimethyl borate 
(B(OCH.sub.3).sub.3) in 6.5 ml dry benzene was added into the solution in 
the flask using a syringe with stirring. The resulting mixture was reacted 
at 160.degree. C., whereupon the colorless reaction mixture was turned 
light yellow. After completion of the reaction, the solvent was removed in 
vacuo to obtain light yellow solids with a yield of 90% by weight. 
The cryoscopic method using dry benzene as a solvent revealed that the 
polyborosilazane had a number-average molecular weight of 1,550. The 
infrared spectrum of this polymer (solvent: dry benzene) is shown in FIG. 
16. There are absorption peaks based on CH.sub.3 and OCH.sub.3 (at 2,960 
and 2,850 cm.sup.-1), a broad peak based on B-O and B-N (1,300-1,540 
cm.sup.-1) and a peak based on Si-O (1,100 cm.sup.-1) in addition to a 
peak based on NH (3350 cm.sup.-1) and a peak based on Si-H (2,170 
cm.sup.-1). The elementary analysis of the polymer gave the following 
results (in terms of % by weight): 
Si: 43.9, N: 24.7, C: 9.8, 0: 10.6, H: 6.8, B: 4.2 
COMATIVE EXAMPLE 2 
Production of Polyborosilazane 
To a 200 ml four-necked flask equipped with a gas feed conduit, a dropping 
funnel, a thermometer and a magnetic stirrer, a dry nitrogen gas was fed 
for replacing the air therewith. Then, 2.93 g of the 
polymethyl(hydro)silazane obtained in Reference Example 2 and 80 ml of dry 
o-xylene were charged into the flask, into which 1.29 g (12.4 mmol) of 
trimethyl borate (B(OCH.sub.3).sub.3) was added with stirring. The mixture 
was then reacted at 180.degree.-200.degree. C., whereupon the colorless 
reaction mixture was turned light yellow. After completion of the 
reaction, the solvent was removed in vacuo to obtain light yellow solids 
with a yield of 85% by weight. 
The cryoscopic method using dry benzene as a solvent revealed that the 
polyborosilazane had a number-average molecular weight of 1,350. The 
infrared spectrum of this polymer (solvent: dry benzene) is shown in FIG. 
17. There are absorption peaks based on CH.sub.3 and OCH.sub.3 (at 2,960 
and 2,850 cm.sup.-1), a broad peak based on B-O and B-N (1,300-1,540 
cm.sup.-1) and a peak based on Si-O (1,100 cm.sup.-1) in addition to a 
peak based on NH (3350 cm.sup.-1) and a peak based on Si-H (2,170 
cm.sup.-1). The elementary analysis of the polymer gave the following 
results (in terms of % by weight): 
Si: 34.5, N: 19.8, C: 25.5, 0: 11.5, H: 5.5, B: 3.2 
COMATIVE EXAMPLE 3 
Production of Polyhydrotitanosilazane 
To a 200 ml four-necked flask equipped with a gas feed conduit, a dropping 
funnel, a thermometer and a magnetic stirrer, a dry nitrogen gas was fed 
for replacing the air therewith. Then, 110 g of a solution of the 
perhydropolysilazane obtained in Reference Example 1 in benzene 
(concentration of perhydropolysilazane: 4.57% by weight) was charged into 
the flask. A solution of 6.30 g (22.2 mmol) of titanium isopropoxide in 
6.5 ml dry benzene was added into the solution in the flask using a 
syringe with stirring and the mixture was reacted. As a result, the 
colorless reaction mixture was turned brown, purple and finally black. 
After completion of the reaction, the solvent was removed in vacuo to 
obtain polyhydrotitanosilazane with a yield of 84% by weight. 
The cryoscopic method using dry benzene as a solvent revealed that the 
polyhydrotitanosilazane had a number-average molecular weight of 1,840. 
The infrared spectrum of this polymer (solvent: dry benzene) is shown in 
FIG. 18. There are absorption peaks based on (CH.sub.3).sub.2 CH-- (at 
1,365 and 1,335 cm.sup.-1), peaks based on (C-O)Ti (at 1,160, 1,125 and 
1,000 cm.sup.-1), peaks based on SiOTi and (C-O)Ti (at 950-1,100 cm.sup.-1 
and a peak based on Ti-O (615 cm.sup.-1) in addition to a peak based on NH 
(3,350 cm.sup.-1) and a peak based on Si-H (2,170 cm.sup.-1). The 
elementary analysis of the polymer gave the following results (in terms of 
% by weight): 
Si: 33.0, N: 14.0, C: 23.4, 0: 11.8, H: 6.6, Ti: 9.5 
COMATIVE EXAMPLE 4 
Production of Polyhydrotitanosilazane 
To a 200 ml four-necked flask equipped with a gas feed conduit, a dropping 
funnel, a thermometer and a magnetic stirrer, a dry nitrogen gas was fed 
for replacing the air therewith. Then, 2.93 g of the 
polymethyl(hydro)silazane obtained in Reference Example 2 and 80 ml of dry 
o-xylene were charged into the flask, into which 3.46 g (11.9 mmol) of 
titanium isopropoxide were added with stirring and the mixture was reacted 
at a temperature of 130.degree.-135.degree. C. As a result, the colorless 
reaction mixture was turned yellow. After completion of the reaction, the 
solvent was removed in vacuo to obtain polytitanosilazane in the form of 
yellow solids with a yield of 61.6% by weight. 
The cryoscopic method using dry benzene as a solvent revealed that the 
polyhydrotitanosilazane had a number-average molecular weight of 1,510. 
The infrared spectrum of this polymer (solvent: dry benzene) is shown in 
FIG. 19. There are absorption peaks based on (CH.sub.3).sub.2 CH-- (at 
1,360 and 1,330 cm.sup.-1), peaks based on SiOTi and (C-O)Ti (at 1,160, 
1,120 and 995 cm.sup.-1) and a peak based on Ti-O (615 cm.sup.-1) in 
addition to a peak based on NH (3,380 cm.sup.-1) and a peak based on Si-H 
(2,120 cm.sup.-1). The elementary analysis of the polymer gave the 
following results (in terms of % by weight): 
Si: 36.4, N: 17.8, C: 27.1, 0: 6.6, H: 5.9, Ti: 5.3 
COMATIVE EXAMPLE 5 
Production of Polyhydroaluminosilazane 
To a 200 ml four-necked flask equipped with a gas feed conduit, a dropping 
funnel, a thermometer and a magnetic stirrer, a dry nitrogen gas was fed 
for replacing the air therewith. Then, 1.50 g (7.34 mmol) of aluminum 
isopropoxide were charged into the flask, into which 83 ml of a solution 
of the perhydropolysilazane obtained in Reference Example 1 in benzene 
(concentration of perhydropolysilazane: 40.72 g/l) was added using a 
syringe with stirring. The mixture was reacted at 80.degree. C. under 
reflux in the atmosphere of argon for 2 hours, whereupon the colorless 
reaction mixture was turned light yellow. After completion of the 
reaction, the solvent was removed in vacuo to obtain 
polyhydroaluminosilazane with a yield of 89% by weight. 
The cryoscopic method using dry benzene as a solvent revealed that the 
polyhydroaluminosilazane had a number-average molecular weight of 1,710. 
The infrared spectrum of this polymer (solvent: dry benzene) is shown in 
FIG. 20. There are absorption peaks based on (C-O)A1 (at 1,380 and 1,200 
cm.sup.-1) and based on SiOAl (at 1,100 cm.sup.-1) in addition to peaks 
based on NH (3,350 cm.sup.-1) and based on Si-H (2,170 cm.sup.-1). The 
elementary analysis of the polymer gave the following results (in terms of 
% by weight): 
Si: 45.6, N: 23.9, C: 12.8, 0: 8.8, H: 5.5, Al: 4.4 
COMATIVE EXAMPLE 6 
Production of Polyaluminosilazane 
To a 500 ml four-necked flask equipped with a gas feed conduit, a dropping 
funnel, a thermometer and a magnetic stirrer, a dry nitrogen gas was fed 
for replacing the air therewith. Then, 4.5 g (22.0 mmol) of aluminum 
isopropoxide were charged into the flask, into which 300 ml of a solution 
of the polymethylhydrosilazane obtained in Reference Example 2 in o-xylene 
(concentration of polysilazane: 20.4 g/l) was added using a syringe with 
stirring. The mixture was reacted at 130.degree. C. under reflux in the 
atmosphere of nitrogen for 48 hours, whereupon the colorless reaction 
mixture was turned light yellow. After completion of the reaction, the 
solvent was removed in vacuo to obtain polyaluminosilazane with a yield of 
75% by weight. 
The cryoscopic method using dry benzene as a solvent revealed that the 
polyaluminosilazane had a number-average molecular weight of 1,500. The 
infrared spectrum of this polymer (solvent: dry benzene) is shown in FIG. 
21. There are absorption peaks based on NH (3,350 cm.sup.-1) and based on 
Si-H (2,170 cm.sup.-1). The elementary analysis of the polymer gave the 
following results (in terms of % by weight): 
Si: 35.8, N: 17.5, C: 26.6, O: 8.7, H: 6.1, Al: 4.61 
COMATIVE EXAMPLE 7 
Production of Polyzirconosilazane 
To a 100 ml four-necked flask equipped with a gas feed conduit, a dropping 
funnel, a thermometer and a magnetic stirrer, a dry nitrogen gas was fed 
for replacing the air therewith. Then, 63.4 g of a solution of the 
perhydropolysilazane obtained in Reference Example 1 in o-xylene 
(concentration of perhydropolysilazane: 4.45% by weight) were charged into 
the flask. A solution of 4.00 g (12.2 mmol) of zirconium isopropoxide 
dissolved in 6.0 ml dry benzene was added into the solution in the flask 
using a syringe with stirring. The resulting mixture was reacted at 
90.degree. C. in the atmosphere of nitrogen, whereupon the colorless 
reaction mixture was turned light yellow. After completion of the 
reaction, the solvent was removed in vacuo to obtain polyzirconosilazane. 
The cryoscopic method using dry benzene as a solvent revealed that the 
polyzirconosilazane had a number-average molecular weight of 2,100. The 
infrared spectrum of this polymer (solvent: dry benzene) is shown in FIG. 
22. There are absorption peaks based on (CH.sub.3)2CH- (at 1,365 and 1,335 
cm.sup.-1), peaks based on (C-O)Zr (at 1,170) and a peak based on SiOZr 
and (C-O)Zr (at 950 cm.sup.-1) in addition to a peak based on NH (3350 
cm.sup.-1) and a peak based on Si-H (2,170 cm.sup.-1). The elementary 
analysis of the polymer gave the following results (in terms of % by 
weight): 
Si: 34.0, N: 13.0, C: 14.4, O: 13.2, H: 5.1, Zr: 18.6 
COMATIVE EXAMPLE 8 
Production of Polyzirconosilazane 
To a 500 ml four-necked flask equipped with a gas feed conduit, a dropping 
funnel, a thermometer and a magnetic stirrer, a dry nitrogen gas was fed 
for replacing the air therewith. Then, 7.33 g of the 
polymethyl(hydro)silazane obtained in Reference Example 2 and 250 ml of 
dry o-xylene were charged into the flask, into which 11.4 g (34.7 mmol) of 
zirconium isopropoxide were added with stirring. The mixture was then 
reacted at 130.degree.-135.degree. C. After completion of the reaction, 
the solvent was removed in vacuo to obtain polyzirconosilazane. 
The cryoscopic method using dry benzene as a solvent revealed that the 
polyzirconosilazane had a number-average molecular weight of 1,750. The 
infrared spectrum of this polymer (solvent: dry benzene) is shown in FIG. 
23. There are absorption peaks based on (CH.sub.3)2CH-- (at 1,360 and 
1,340 cm.sup.-1) and peaks based on (C-O)Zr (at 1,170 and 1,000 cm.sup.-1) 
in addition to a peak based on NH (3,380 cm.sup.-1) and a peak based on 
Si-H (2,120 cm.sup.-1). The elementary analysis of the polymer gave the 
following results (in terms of % by weight): 
Si: 28.0, N: 13.5, C: 27.5, O: 9.0, H: 5.4, Zr: 14.6 
EXAMPLE 1 
Production of Polyborosilazane 
To a 500 ml four-necked flask equipped with a gas feed conduit, a dropping 
funnel, a thermometer and a magnetic stirrer, a dry nitrogen gas was fed 
for replacing the air therewith. Then, 110 g of a solution of the 
perhydropolysilazane obtained in Reference Example 1 in benzene 
(concentration of perhydropolysilazane: 4.57% by weight) was charged into 
the flask. A solution of 29.0 g (279 mmol) of trimethyl borate 
(B(OCH.sub.3)3) in 6.5 ml dry benzene was added into the solution in the 
flask using a syringe with stirring and, further, 134.8 g (837 mmol) of 
hexamethyldisilazane ((CH.sub.3).sub.3 SiNHSi(CH.sub.3).sub.3)) were added 
into the flask using a syringe. The resulting mixture was reacted at 
160.degree. C., whereupon the colorless reaction mixture was turned light 
yellow. After completion of the reaction, the solvent was removed in vacuo 
to obtain light yellow solids with a yield of 95% by weight. 
The cryoscopic method using dry benzene as a solvent revealed that the 
polyborosilazane had a number-average molecular weight of 1,810. The 
infrared spectrum of this polymer (solvent: dry benzene) is shown in FIG. 
1. There are absorption peaks based on CH.sub.3 and OCH.sub.3 (at 2,960 
and 2,850 cm.sup.-1) and a broad peak based on B-O and B-N (1,300-1,540 
cm.sup.-1) in addition to a peak based on NH (3,350 cm.sup.-1) and a peak 
based on Si-H (2,170 cm.sup.-1). No absorption peak based on Si-o is 
observed at 1,100 cm.sup.-1. The elementary analysis of the polymer gave 
the following results (in terms of % by weight): 
Si: 46.3, N: 28.3, C: 9.6, 0: 3.8, H: 7.5, B: 4.5 
Production of Ceramics 
Part of the thus obtained polyborosilazane was dissolved in toluene and the 
solution was adjusted to a predetermined concentration. The solution was 
then poured into a mold cavity of a mold formed of a tetrafluoroethylene. 
Then the solvent was removed at 200.degree. C. under a nitrogen stream to 
obtain a transparent shaped mass having a size of 20 mmo.times.10 mm. This 
was heated to 1,000.degree. C. in the atmosphere of ammonia at a heating 
rate of 1.degree. C./min and then to 1,600.degree. C. in a nitrogen 
atmosphere at a heating rate of 10.degree. C./min, and further maintained 
at that temperature for 10 hours, thereby obtaining white, disk-like 
ceramic body. Elementary analysis of the shaped ceramic body gave the 
following results (in terms of % by weight): 
Si: 50.2, N: 39.1, C: 1.5, O: 4.1, B: 5.1 
Powder X-ray diffraction analysis revealed that the shaped body was 
amorphous. The shaped body had a three-point bending strength of 5.6 MPa. 
Another part of the polyborosilazane obtained above was processed to obtain 
ceramic fibers. Thus, the polyborosilazane was dissolved in xylene and the 
solvent was removed in vacuo. The removal of the solvent was stopped when 
the solution had desired spinnability. The resultant solution was charged 
in a defoaming vessel of a dry-spinning device and maintained in quiescent 
state at 60.degree. C. for about 2 hours to effect defoaming. Then, the 
solution was injected at 30.degree. C. through a nozzle having a nozzle 
diameter of 0.1 mm into a cylinder maintained at 130.degree. C. under 
ambient dry air, and the spun fiber was taken up at a speed of 300 m/min 
on a bobbin, thereby obtaining a fiber having an average diameter of 12 
.mu.m. While applying a tension of 500 g/mm.sup.2, this fiber was heated 
from room temperature to 1,000.degree. C. at a heating rate of 1.degree. 
C./min in an ammoniacal atmosphere and then to 1,600.degree. C. at a 
heating rate of 10.degree. C./min in a nitrogen atmosphere and maintained 
at 1,600.degree. C. for 1 hour to effect pyrolysis, thereby obtaining 
ceramic fiber. This fiber was found to have a tensile strength of 130-450 
kgf/mm.sup.2 (average: 200 kgf/mm.sup.2. Elementary analysis of the 
ceramic fiber gave the following results (in terms of % by weight): 
Si: 50.0, N: 38.1, C: 1.5, O: 5.4, B: 5.0 
EXAMPLE 2 
Production of Polyborosilazane 
To a 500 ml four-necked flask equipped with a gas feed conduit, a dropping 
funnel, a thermometer and a magnetic stirrer, a dry nitrogen gas was fed 
for replacing the air therewith. Then, 110 g of a solution of the 
perhydropolysilazane obtained in Reference Example 1 in benzene 
(concentration of perhydropolysilazane: 4.57% by weight) was charged into 
the flask. A solution of 29.0 g (279 mmol) of trimethyl borate 
(B(OCH.sub.3).sub.3) in 6.5 ml dry benzene was added into the solution in 
the flask using a syringe with stirring and, further, 90.8 g (837 mmol) of 
trimethylchlorosilane ((CH.sub.3).sub.3 SiCl) were added into the flask 
using a syringe. The resulting mixture was reacted at 160.degree. C., 
whereupon the colorless reaction mixture was turned light yellow. After 
completion of the reaction, the solvent was removed in vacuo to obtain 
light yellow solids with a yield of 94% by weight. 
The cryoscopic method using dry benzene as a solvent revealed that the 
polyborosilazane had a number-average molecular weight of 1,900. The 
infrared spectrum of this polymer (solvent: dry benzene) is shown in FIG. 
2. There are absorption peaks based on CH.sub.3 and OCH.sub.3 (at 2,960 
and 2,850 cm.sup.-1) and peaks based on B-O and B-N (1,300-1,540 
cm.sup.-1) in addition to a peak based on NH (3,350 cm.sup.-1) and a peak 
based on Si-H (2,170 cm.sup.-1). No absorption peak based on Si-O is 
observed at 1,100 cm.sup.-1. The elementary analysis of the polymer gave 
the following results (in terms of % by weight): 
Si: 45.1, N: 27.2, C: 11.7, O: 4.1, H: 7.2, B: 4.4 
Production of Ceramics 
Part of the thus obtained polyborosilazane was dissolved in toluene and the 
solution was adjusted to a predetermined concentration. The solution was 
then poured into a mold cavity of a mold formed of a tetrafluoroethylene. 
Then the solvent was removed at 200.degree. C. under a nitrogen stream to 
obtain a transparent shaped mass having a size of 20 mmo.times.10 mm. This 
was heated to 1,000.degree. C. in the atmosphere of ammonia at a heating 
rate of 1.degree. C./min and then to 1,600.degree. C. in a nitrogen 
atmosphere at a heating rate of 10.degree. C./min, and further maintained 
at that temperature for 10 hours, thereby obtaining white, disk-like 
ceramic body. Elementary analysis of the shaped ceramic body gave the 
following results (in terms of % by weight): 
Si: 49.1, N: 39.6, C: 2.5, O: 4.2, B: 4.6 
Powder X-ray diffraction analysis revealed that the shaped body was 
amorphous. The shaped body had a three-point bending strength of 4.3 MPa. 
EXAMPLE 3 
Production of Polyborosilazane 
To a 500 ml four-necked flask equipped with a gas feed conduit, a dropping 
funnel, a thermometer and a magnetic stirrer, a dry nitrogen gas was fed 
for replacing the air therewith. Then, 110 g of a solution of the 
perhydropolysilazane obtained in Reference Example 1 in benzene 
(concentration of perhydropolysilazane: 4.57% by weight) was charged into 
the flask. A solution of 29.0 g (279 mmol) of trimethyl borate 
(B(OCH.sub.3).sub.3) in 6.5 ml dry benzene was added into the solution in 
the flask using a syringe with stirring and, further, 98.0 g (837 mmol) of 
trimethylsilylamine ((CH.sub.3).sub.3 SiNH.sub.2) were added into the 
flask using a syringe. The resulting mixture was reacted at 160.degree. 
C., whereupon the colorless reaction mixture was turned light yellow. 
After completion of the reaction, the solvent was removed in vacuo to 
obtain light yellow solids with a yield of 95% by weight. 
The cryoscopic method using dry benzene as a solvent revealed that the 
polyborosilazane had a number-average molecular weight of 1,860. The 
infrared spectrum of this polymer (solvent: dry benzene) is shown in FIG. 
3. There are absorption peaks based on CH.sub.3 and OCH.sub.3 (at 2,960 
and 2,850 cm.sup.-1) and peaks based on B-O and B-N (1,300-1,540 
cm.sup.-1) in addition to a peak based on NH (3,350 cm.sup.-1) and a peak 
based on Si-H (2,170 cm.sup.-1). No absorption peak based on Si-O is 
observed at 1,100 cm.sup.-1. The elementary analysis of the polymer gave 
the following results (in terms of % by weight): 
Si: 45.9, N: 29.5, C: 10.1, O: 3.0, H: 7.0, B: 4.5 
Production of Ceramics 
Part of the thus obtained polyborosilazane was dissolved in toluene and the 
solution was adjusted to a predetermined concentration. The solution was 
then poured into a mold cavity of a mold formed of a tetrafluoroethylene. 
Then the solvent was removed at 200.degree. C. under a nitrogen stream to 
obtain a transparent shaped mass having a size of 20 mmo.times.10 mm. This 
was heated to 1,000.degree. C. in the atmosphere of ammonia at a heating 
rate of 1.degree. C./min and then to 1,600.degree. C. in a nitrogen 
atmosphere at a heating rate of 10.degree. C./min, and further maintained 
at that temperature for 10 hours, thereby obtaining white, disk-like 
ceramic body. Elementary analysis of the shaped ceramic body gave the 
following results (in terms of % by weight): 
Si: 50.5, N: 40.6, C: 1.1, O: 3.2, B: 4.6 
Powder X-ray diffraction analysis revealed that the shaped body was 
amorphous. The shaped body had a three-point bending strength of 5.6 MPa. 
EXAMPLE 4 
Production of Polyborosilazane 
To a 500 ml four-necked flask equipped with a gas feed conduit, a dropping 
funnel, a thermometer and a magnetic stirrer, a dry nitrogen gas was fed 
for replacing the air therewith. Then, 110 g of a solution of the 
perhydropolysilazane obtained in Reference Example 1 in benzene 
(concentration of perhydropolysilazane: 4.57% by weight) was charged into 
the flask. A solution of 29.0 g (279 mmol) of trimethyl borate 
(B(OCH.sub.3).sub.3) in 6.5 ml dry benzene was added into the solution in 
the flask using a syringe with stirring and, further, 192.5 g (837 mmol) 
of hexaethyldisilane ((C.sub.2 H.sub.5).sub.3 Si.sub.2 (C.sub.2 
H.sub.5).sub.3) were added into the flask using a syringe. The resulting 
mixture was reacted 160.degree. C., whereupon the colorless reaction 
mixture was turned light yellow. After completion of the reaction, the 
solvent was removed in vacuo to obtain light yellow solids with a yield of 
90% by weight. 
The cryoscopic method using dry benzene as a solvent revealed that the 
polyborosilazane had a number-average molecular weight of 1,750. The 
infrared spectrum of this polymer (solvent: dry benzene) is shown in FIG. 
4. There are absorption peaks based on CH.sub.3 and OCH.sub.3 (at 2,960 
and 2,850 cm.sup.-1) and peaks based on B-O and B-N (1,300-1,540 
cm.sup.-1) in addition to a peak based on NH (3,350 cm.sup.-1) and a peak 
based on Si-H (2,170 cm.sup.-1). No absorption peak based on Si-O is 
observed at 1,100 cm.sup.-1. The elementary analysis of the polymer gave 
the following results (in terms of % by weight): 
Si: 45.0, N: 28.1, C: 11.1, O: 4.5, H: 6.9, B: 4.4 
Production of Ceramics 
Part of the thus obtained polyborosilazane was dissolved in toluene and the 
solution was adjusted to a predetermined concentration. The solution was 
then poured into a mold cavity of a mold formed of a tetrafluoroethylene. 
Then the solvent was removed at 200.degree. C. under a nitrogen stream to 
obtain a transparent shaped mass having a size of 20 mmo.times.10 mm. This 
was heated to 1,000.degree. C. in the atmosphere of ammonia at a heating 
rate of 1.degree. C./min and then to 1,600.degree. C. in a nitrogen 
atmosphere at a heating rate of 10.degree. C./min, and further maintained 
at that temperature for 10 hours, thereby obtaining white, disk-like 
ceramic body. Elementary analysis of the shaped ceramic body gave the 
following results (in terms of % by weight): 
Si: 50.0, N: 38.9, C: 2.0, O: 4.6, B: 4.5 
Powder X-ray diffraction analysis revealed that the shaped body was 
amorphous. The shaped body had a three-point bending strength of 7.9 MPa. 
EXAMPLE 5 
Production of Polyborosilazane 
To a 500 ml four-necked flask equipped with a gas feed conduit, a dropping 
funnel, a thermometer and a magnetic stirrer, a dry nitrogen gas was fed 
for replacing the air therewith. Then, 2.93 g of the 
polymethyl(hydro)silazane obtained in Reference Example 2 and 80 ml of dry 
o-xylene were charged into the flask, into which 1.29 g (12.4 mmol) of 
trimethyl borate (B(OCH.sub.3).sub.3) was added with stirring and, 
further, 3.87 g (37.2 mmol) of hexamethyldisilazane ((CH.sub.3).sub.3 
SiNHSi(CH.sub.3).sub.3)) were added into the flask using a syringe. The 
mixture was then reacted at 200.degree. C., whereupon the colorless 
reaction mixture was turned light yellow. After completion of the 
reaction, the solvent was removed in vacuo to obtain light yellow solids 
with a yield of 92% by weight. 
The cryoscopic method using dry benzene as a solvent revealed that the 
polyborosilazane had a number-average molecular weight of 2,100. The 
infrared spectrum of this polymer (solvent: dry benzene) is shown in FIG. 
5. There are absorption peaks based on CH.sub.3 and OCH.sub.3 (at 2,960 
and 2,850 cm.sup.-1) and peaks based on B-O and B-N (1,300-1,540 
cm.sup.-1) in addition to a peak based on NH (3350 cm.sup.-1) and a peak 
based on Si-H (2,170 cm.sup.-1). No peak based on Si-O (1,100 cm.sup.-1) 
was observed. The elementary analysis of the polymer gave the following 
results (in terms of % by weight): 
Si: 35.5, N: 20.5, C: 31.5, O: 3.0, H: 6.2, B: 3.3 
Production of Ceramics 
Part of the thus obtained polyborosilazane was dissolved in toluene and the 
solution was adjusted to a predetermined concentration. The solution was 
then poured into a mold cavity of a mold formed of a tetrafluoroethylene. 
Then the solvent was removed at 200.degree. C. under a nitrogen stream to 
obtain a transparent shaped mass having a size of 20 mmo.times.10 mm. This 
was heated to 1,000.degree. C. in the atmosphere of ammonia at a heating 
rate of 1.degree. C./min and then to 1,600.degree. C. in a nitrogen 
atmosphere at a heating rate of 10.degree. C./min, and further maintained 
at that temperature for 10 hours, thereby obtaining white, disk-like 
ceramic body. Elementary analysis of the shaped ceramic body gave the 
following results (in terms of % by weight): 
Si: 47.6, N: 36.8, C: 8.5, O: 3.2, B: 3.9 
Powder X-ray diffraction analysis revealed that the shaped body was 
amorphous. The shaped body had a three-point bending strength of 5.0 MPa. 
Another part of the polyborosilazane obtained above was processed to obtain 
ceramic fibers. Thus, the polyborosilazane was dissolved in xylene and the 
solvent was removed in vacuo. The removal of the solvent was stopped when 
the solution had desired spinnability. The resultant solution was charged 
in a defoaming vessel of a dry-spinning device and maintained in quiescent 
state at 60.degree. C. for about 2 hours to effect defoaming. Then, the 
solution was injected at 30.degree. C. through a nozzle having a nozzle 
diameter of 0.1 mm into a cylinder maintained at 130.degree. C. under 
ambient dry air, and the spun fiber was taken up at a speed of 300 m/min 
on a bobbin, thereby obtaining a fiber having an average diameter of 12 
.mu.m. While applying a tension of 500 g/mm.sup.2, this fiber was heated 
from room temperature to 1,000.degree. C. at a heating rate of 1.degree. 
C./min in an ammoniacal atmosphere and then to 1,600 .degree. C. at a 
heating rate of 10.degree. C./min in a nitrogen atmosphere and maintained 
at 1,600.degree. C. for 1 hour to effect pyrolysis, thereby obtaining 
ceramic fiber. This fiber was found to have a tensile strength of 100-390 
kgf/mm.sup.2 (average: 180 kgf/mm.sup.2. Elementary analysis of the 
ceramic fiber gave the following results (in terms of % by weight): 
Si: 48.0, N: 37.6, C: 7.5, O: 6.9, B: 5.0 
EXAMPLE 6 
Production of Polyhydrotitanosilazane 
To a 500 ml four-necked flask equipped with a gas feed conduit, a dropping 
funnel, a thermometer and a magnetic stirrer, a dry nitrogen gas was fed 
for replacing the air therewith. Then, 110 g of a solution of the 
perhydropolysilazane obtained in Reference Example 1 in benzene 
(concentration of perhydropolysilazane: 4.57% by weight) was charged into 
the flask. A solution of 6.30 g (22.2 mmol) of titanium isopropoxide in 
6.5 ml dry benzene was added into the solution in the flask using a 
syringe with stirring and, further, 14.3 g (88.8 mmol) of 
hexamethyldisilazane ((CH.sub.3).sub.3 SiNHSi(CH.sub.3).sub.3)) were added 
into the flask using a syringe. The mixture was then reacted so that the 
colorless reaction mixture was turned brown, purple and finally black. 
After completion of the reaction, the solvent was removed in vacuo to 
obtain polyhydrotitanosilazane with a yield of 92% by weight. 
The cryoscopic method using dry benzene as a solvent revealed that the 
polyhydrotitanosilazane had a number-average molecular weight of 2,100. 
The infrared spectrum of this polymer (solvent: dry benzene) is shown in 
FIG. 6. There are absorption peaks based on (CH.sub.3).sub.2 CH-- (at 
1,365 and 1,335 cm.sup.-1), peaks based on (C-O)Ti (at 1,160, 1,125 and 
1,000 cm.sup.-1), peaks based on (C-O)Ti (at 950 cm.sup.-1 and a peak 
based on Ti-O (615 cm.sup.-1) in addition to a peak based on NH (3,350 
cm.sup.-1) and a peak based on Si-H (2,170 cm.sup.-1). No peak based on 
SiO (1,100 cm.sup.-1) was observed. The elementary analysis of the polymer 
gave the following results (in terms of % by weight): 
Si: 44.2, N: 22.0, C: 11.9, O: 2.9, H: 7.2, Ti: 11.2 
Production of Ceramics 
Part of the thus obtained polyhydrotitanosilazane was dissolved in toluene 
and the solution was adjusted to a predetermined concentration. The 
solution was then poured into a mold cavity of a mold formed of a 
tetrafluoroethylene. Then the solvent was removed at 200.degree. C. under 
a nitrogen stream to obtain a transparent shaped mass having a size of 20 
mmo.times.10 mm. This was heated to 1,000.degree. C. in the atmosphere of 
ammonia at a heating rate of 1.degree. C./min and then to 1,600.degree. C. 
in a hydrogen atmosphere at a heating rate of 10.degree. C./min, and 
further maintained at that temperature for 10 hours, thereby obtaining 
white, disk-like ceramic body. Elementary analysis of the shaped ceramic 
body gave the following results (in terms of % by weight): 
Si: 50.4, N: 32.9, C: 1.6, O: 3.0, Ti: 12.1 
Powder X-ray diffraction analysis revealed that the shaped body was 
amorphous. The shaped body had a three-point bending strength of 10.5 MPa. 
Another part of the polyhydrotitanosilazane obtained above was processed to 
obtain ceramic fibers. Thus, the polyhydrotitanosilazane was dissolved in 
xylene and the solvent was removed in vacuo. The removal of the solvent 
was stopped when the solution had desired spinnability. The resultant 
solution was charged in a defoaming vessel of a dry-spinning device and 
maintained in quiescent state at 60.degree. C. for about 2 hours to effect 
defoaming. Then, the solution was injected at 30.degree. C. through a 
nozzle having a nozzle diameter of 0.1 mm into a cylinder maintained at 
130.degree. C. under ambient dry air, and the spun fiber was taken up at a 
speed of 300 m/min on a bobbin, thereby obtaining a fiber having an 
average diameter of 12 .mu.m. While applying a tension of 500 g/mm.sup.2, 
this fiber was heated from room temperature to 1,000.degree. C. at a 
heating rate of 1.degree. C./min in an ammoniacal atmosphere and then to 
1,600 .degree. C. at a heating rate of 10.degree. C./min in a nitrogen 
atmosphere and maintained at 1,600.degree. C. for 1 hour to effect 
pyrolysis, thereby obtaining ceramic fiber. This fiber was found to have a 
tensile strength of 100-250 kgf/mm.sup.2 (average: 130 kgf/mm.sup.2. 
Elementary analysis of the ceramic fiber gave the following results (in 
terms of % by weight): 
Si: 48.5, N: 37.1, C: 1.5, O: 5.4, Ti: 11.0 
EXAMPLE 7 
Production of Polytitanosilazane 
To a 500 ml four-necked flask equipped with a gas feed conduit, a dropping 
funnel, a thermometer and a magnetic stirrer, a dry nitrogen gas was fed 
for replacing the air therewith. Then, 2.93 g of the 
polymethyl(hydro)silazane obtained in Reference Example 2 and 80 ml of dry 
o-xylene were charged into the flask, into which 3.46 g (11.9 mmol) of 
titanium isopropoxide were added with stirring and, further, 7.67 g (47.6 
mmol) of hexamethyldisilazane ((CH.sub.3).sub.3 SiNHSi(CH.sub.3).sub.3)) 
were added into the flask using a syringe. The mixture was reacted at a 
temperature of 130.degree.-135.degree. C., whereupon the colorless 
reaction mixture was turned yellow. After completion of the reaction, the 
solvent was removed in vacuo to obtain light yellow solids with a yield of 
80% by weight. 
The cryoscopic method using dry benzene as a solvent revealed that the 
polyborosilazane had a number-average molecular weight of 1,870. The 
infrared spectrum of this polymer (solvent: dry benzene) is shown in FIG. 
7. There are absorption peaks based on (CH.sub.3).sub.2 CH-- (at 1,365 and 
1,335 cm.sup.-1), peaks based on (C-O)Ti (at 995 cm.sup.-1) and a peak 
based on Ti-O (615 cm.sup.-1) in addition to a peak based on NH (3,380 
cm.sup.-1) and a peak based on Si-H (2,120 cm.sup.-1). No peak based on 
SiO (1,100 cm.sup.-1) was observed. The elementary analysis of the polymer 
gave the following results (in terms of % by weight): 
Si: 48.5, N: 25.0, C: 12.2, O: 2.0, H: 6.2, Ti: 6.1 
Production of Ceramics 
Part of the thus obtained polytitanosilazane was dissolved in toluene and 
the solution was adjusted to a predetermined concentration. The solution 
was then poured into a mold cavity of a mold formed of a 
tetrafluoroethylene. Then the solvent was removed at 200.degree. C. under 
a nitrogen stream to obtain a transparent shaped mass having a size of 20 
mmo.times.10 mm. This was heated to 1,000.degree. C. in the atmosphere of 
ammonia at a heating rate of 1.degree. C./min and then to 1,600.degree. C. 
in a nitrogen atmosphere at a heating rate of 10.degree. C./min, and 
further maintained at that temperature for 10 hours, thereby obtaining 
white, disk-like ceramic body. Elementary analysis of the shaped ceramic 
body gave the following results (in terms of % by weight): 
Si: 51.7, N: 36.8, C: 2.0, O: 2.3, Ti: 7.2 
Powder X-ray diffraction analysis revealed that the shaped body was 
amorphous. The shaped body had a three-point bending strength of 5.9 MPa. 
Another part of the polytitanosilazane obtained above was processed to 
obtain ceramic fibers. Thus, the polyborosilazane was dissolved in xylene 
and the solvent was removed in vacuo. The removal of the solvent was 
stopped when the solution had desired spinnability. The resultant solution 
was charged in a defoaming vessel of a dry-spinning device and maintained 
in quiescent state at 60.degree. C. for about 2 hours to effect defoaming. 
Then, the solution was injected at 30.degree. C. through a nozzle having a 
nozzle diameter of 0.1 mm into a cylinder maintained at 130.degree. C. 
under ambient dry air, and the spun fiber was taken up at a speed of 300 
m/min on a bobbin, thereby obtaining a fiber having an average diameter of 
12 .mu.m. While applying a tension of 500 g/mm.sup.2, this fiber was 
heated from room temperature to 1,000.degree. C. at a heating rate of 
1.degree. C./min in an ammoniacal atmosphere and then to 1,600 .degree. C. 
at a heating rate of 10.degree. C./min in a nitrogen atmosphere and 
maintained at 1,600.degree. C. for 1 hour to effect pyrolysis, thereby 
obtaining ceramic fiber. This fiber was found to have a tensile strength 
of 130-280 kgf/mm.sup.2 (average: 160 kgf/mm.sup.2. Elementary analysis of 
the ceramic fiber gave the following results (in terms of % by weight): 
Si: 46.5, N: 35.1, C: 3.5, O: 5.0, Ti: 7.0 
EXAMPLE 8 
Production of polyhydroaluminosilazane 
To a 500 ml four-necked flask equipped with a gas feed conduit, a dropping 
funnel, a thermometer and a magnetic stirrer, a dry nitrogen gas was fed 
for replacing the air therewith. Then, 1.50 g (7.34 mmol) of aluminum 
isopropoxide were charged into the flask, into which 83 ml of a solution 
of the perhydropolysilazane obtained in Reference Example 1 in benzene 
(concentration of perhydropolysilazane: 40.72 g/l) was added using a 
syringe with stirring and, further, 3.55 g (22.0 mmol) of 
hexamethyldisilazane ((CH.sub.3).sub.3 SiNHSi(CH.sub.3).sub.3)) were added 
into the flask using a syringe. The mixture was then reacted at 80.degree. 
C. for 2 hours under reflux in the atmosphere of argon so that the 
colorless reaction mixture was turned light yellow. After completion of 
the reaction, the solvent was removed in vacuo to obtain 
polyhydroaluminosilazane with a yield of 92% by weight. 
The cryoscopic method using dry benzene as a solvent revealed that the 
polyhydroaluminosilazane had a number-average molecular weight of 2,150. 
The infrared spectrum of this polymer (solvent: dry benzene) is shown in 
FIG. 8. There are absorption peaks based on (C-O)Al (at 1,380 and 1,200 
cm.sup.-1) in addition to a peak based on NH (3,350 cm.sup.-1) and a peak 
based on Si-H (2,170 cm.sup.-1). No peak based on SiO (1,100 cm.sup.-1) 
was observed. The elementary analysis of the polymer gave the following 
results (in terms of % by weight): 
Si: 51.1, N: 25.6, C: 8.5, O: 2.9, H: 7.0, Al: 4.9 
Production of Ceramics 
Part of the thus obtained polyhydroaluminosilazane was dissolved in toluene 
and the solution was adjusted to a predetermined concentration. The 
solution was then poured into a mold cavity of a mold formed of a 
tetrafluoroethylene. Then the solvent was removed at 200.degree. C. under 
a nitrogen stream to obtain a transparent shaped mass having a size of 20 
mmo.times.10 mm. This was heated to 1,000.degree. C. in the atmosphere of 
ammonia at a heating rate of 1.degree. C./min and then to 1,600.degree. C. 
in a nitrogen atmosphere at a heating rate of 10.degree. C./min, and 
further maintained at that temperature for 10 hours, thereby obtaining 
white, disk-like ceramic body. Elementary analysis of the shaped ceramic 
body gave the following results (in terms of % by weight): 
Si: 51.7, N: 38.9, C: 0.9, 0: 3.5, Al: 5.0 
Powder X-ray diffraction analysis revealed that the shaped body was 
amorphous. The shaped body had a three-point bending strength of 6.9 MPa. 
EXAMPLE 9 
Production of Polyaluminosilazane 
To a 500 ml four-necked flask equipped with a gas feed conduit, a dropping 
funnel, a thermometer and a magnetic stirrer, a dry nitrogen gas was fed 
for replacing the air therewith. Then, 4.5 g (22.0 mmol) of aluminum 
isopropoxide were charged into the flask, into which 300 ml of a solution 
of the polymethylhydrosilazane obtained in Reference Example 2 in o-xylene 
(concentration of polysilazane: 20.4 g/l) was added using a syringe with 
stirring and, further, 10.6 g (66.0 mmol) of hexamethyldisilazane 
((CH.sub.3).sub.3 SiNHSi(CH.sub.3).sub.3)) were added into the flask using 
a syringe. The mixture was refluxed at a temperature of 130.degree. for 48 
hours with stirring in the atmosphere of nitrogen, whereupon the colorless 
reaction mixture was turned light yellow. After completion of the 
reaction, the solvent was removed in vacuo to obtain light yellow solids 
with a yield of 88% by weight. 
The cryoscopic method using dry benzene as a solvent revealed that the 
polyaluminosilazane had a number-average molecular weight of 1,920. The 
infrared spectrum of this polymer (solvent: dry benzene) is shown in FIG. 
9. There are absorption peaks based on NH (3,350 cm.sup.-1) and based on 
Si-H (2,170 cm.sup.-1). No peak based on SiO (1,100 cm.sup.-1) was 
observed. The elementary analysis of the polymer gave the following 
results (in terms of % by weight): 
Si: 41.7, N: 20.5, C: 24.2, O: 2.8, H: 6.1, Al: 4.7 
Production of Ceramics 
Part of the thus obtained polyaluminonosilazane was dissolved in toluene 
and the solution was adjusted to a predetermined concentration. The 
solution was then poured into a mold cavity of a mold formed of a 
tetrafluoroethylene, Then the solvent was removed at 200.degree. C. under 
a nitrogen stream to obtain a transparent shaped mass having a size of 20 
mmo.times.10 mm. This was heated to 1,000.degree. C. in the atmosphere of 
ammonia at a heating rate of 1.degree. C./min and then to 1,600.degree. C. 
in a nitrogen atmosphere at a heating rate of 10.degree. C./min, and 
further maintained at that temperature for 10 hours, thereby obtaining 
white, disk-like ceramic body. Elementary analysis of the shaped ceramic 
body gave the following results (in terms of % by weight): 
Si: 45.6, N: 42.2, C: 3.5, O: 2.9, Al: 5.8 
Powder X-ray diffraction analysis revealed that the shaped body was 
amorphous. The shaped body had a three-point bending strength of 3.5 MPa. 
EXAMPLE 10 
Production of Polyzirconosilazane 
To a 200 ml four-necked flask equipped with a gas feed conduit, a dropping 
funnel, a thermometer and a magnetic stirrer, a dry nitrogen gas was fed 
for replacing the air therewith. Then, 63.4 g of a solution of the 
perhydropolysilazane obtained in Reference Example 1 in o-xylene 
(concentration of perhydropolysilazane: 4.45% by 9 weight) were charged 
into the flask. A solution of 4.00 g (12.2 mmol) of zirconium isopropoxide 
dissolved in 6.0 ml dry benzene was added into the solution in the flask 
using a syringe with stirring and, further, 7.86 g (48.8 mmol) of 
hexamethyldisilazane ((CH.sub.3).sub.3 SiNHSi(CH.sub.3).sub.3)) were added 
into the flask using a syringe. The mixture was then reacted at 90.degree. 
C. in the atmosphere of dry nitrogen so that the colorless reaction 
mixture was turned light yellow. After completion of the reaction, the 
solvent was removed in vacuo to obtain polyzirconosilazane. 
The cryoscopic method using dry benzene as a solvent revealed that the 
polyzirconosilazane had a number-average molecular weight of 2,440. The 
infrared spectrum of this polymer (solvent: dry benzene) is shown in FIG. 
10. There are absorption peaks based on (CH.sub.3).sub.2 CH-- (at 1,365 
and 1,335 cm.sup.-1), peaks based on (C-O)Zr (at 1,170 cm.sup.-1) and 
peaks based on Si-0-Zr and (C-O)Zr (950 cm.sup.-1) in addition to a peak 
based on NH (3,350 cm.sup.-1) and a peak based on Si-H (2,170 cm.sup.-1). 
The elementary analysis of the polymer gave the following results (in 
terms of % by weight): 
Si: 40.8, N: 21.5, C: 8.5, O: 3.3, H: 6.8, Zr: 19.1 
Production of Ceramics 
Part of the thus obtained polyzirconosilazane was dissolved in toluene and 
the solution was adjusted to a predetermined concentration. The solution 
was then poured into a mold cavity of a mold formed of a 
tetrafluoroethylene. Then the solvent was removed at 200.degree. C. under 
a nitrogen stream to obtain a transparent shaped mass having a size of 20 
mmo.times. 10 mm. This was heated to 1,000.degree. C. in the atmosphere of 
ammonia at a heating rate of 1.degree. C./min and then to 1,600.degree. C. 
in a nitrogen atmosphere at a heating rate of 10.degree. C./min, and 
further maintained at that temperature for 10 hours, thereby obtaining 
white, disk-like ceramic body. Elementary analysis of the shaped ceramic 
body gave the following results (in terms of % by weight): 
Si: 45.0, N: 28.5, C: 0.5, O: 3.5, Zr: 22.5 
Powder X-ray diffraction analysis revealed that the shaped body was 
amorphous. The shaped body had a three-point bending strength of 6.6 MPa. 
EXAMPLE 11 
Production of Polyzirconosilazane 
To a 500 ml four-necked flask equipped with a gas feed conduit, a dropping 
funnel, a thermometer and a magnetic stirrer, a dry nitrogen gas was fed 
for replacing the air therewith. Then, 7.33 g of the 
polymethyl(hydro)silazane obtained in Reference Example 2 and 250 ml of 
dry o-xylene were charged into the flask, into which 11.4 g (34.7 mmol) of 
zirconium isopropoxide were added with stirring and, further, 22.3 g 
(138.8 mmol) of hexamethyldisilazane ((CH.sub.3).sub.3 
SiNHSi(CH.sub.3).sub.3)) were added into the flask using a syringe. The 
mixture was then reacted at 130.degree.-135.degree. C. After completion of 
the reaction, the solvent was removed in vacuo to obtain 
polyzirconosilazane. 
The cryoscopic method using dry benzene as a solvent revealed that the 
polyzirconosilazane had a number-average molecular weight of 2,000. The 
infrared spectrum of this polymer (solvent: dry benzene) is shown in FIG. 
11. There are absorption peaks based on (CH.sub.3).sub.2 CH-- (at 1,360 
and 1,340 cm.sup.-1) and peaks based on (C-O)Zr (at 1,170 and 1,000 
cm.sup.-1) in addition to a peak based on NH (3,380 cm.sup.-1) and a peak 
based on Si-H (2,120 cm.sup.-1). The elementary analysis of the polymer 
gave the following results (in terms of % by weight): 
Si: 33.0, N: 18.1, C: 25.5, O: 2.1, H: 6.1, Zr: 15.2 
Production of Ceramics 
Part of the thus obtained polyzirconosilazane was dissolved in toluene and 
the solution was adjusted to a predetermined concentration. The solution 
was then poured into a mold cavity of a mold formed of a 
tetrafluoroethylene. Then the solvent was removed at 200.degree. C. under 
a nitrogen stream to obtain a transparent shaped mass having a size of 20 
mmo.times.10 mm. This was heated to 1,000.degree. C. in the atmosphere of 
ammonia at a heating rate of 1.degree. C./min and then to 1,600.degree. C. 
in an nitrogen atmosphere at a heating rate of 10.degree. C./min, and 
further maintained at that temperature for 10 hours, thereby obtaining 
white, disk-like ceramic body. Elementary analysis of the shaped ceramic 
body gave the following results (in terms of % by weight): 
Si: 47.4, N: 29.2, C: 6.2, O: 2.3, Zr: 14.9 
Powder X-ray diffraction analysis revealed that the shaped body was 
amorphous. The shaped body had a three-point bending strength of 10.2 MPa.