Lanthanide/phosphorus precursor compositions for MOCVD of lanthanide/phosphorus oxide films

A precursor composition useful for vapor deposition formation of lanthanide metal/phosphorus oxide films, comprising a precursor compound selected from the group consisting of: (i) adducts of the formula MA.sub.3 (L).sub.x ; (ii) phosphido complexes of the formulae M(PR.sub.3).sub.3 or M(PR.sub.3).sub.3 L.sub.x ; and (iii) disubstituted phosphate complexes of the formulae A.sub.2 M(O.sub.2 P(OR).sub.2), AM(O.sub.2 P(OR).sub.2).sub.2, and M(O.sub.2 P(OR).sub.2).sub.3, wherein: x is from 1 to 5, A=Cp or .beta.-diketonate, Cp=cyclopentadienyl, methylcyclopentadienyl, or TMS-cyclopentadienyl, R=C.sub.1 -C.sub.8 alkyl, and L=a phosphorus-containing ligand selected from the group consisting of phosphine, phosphine oxide, phosphite, phosphate, and 1,2-bis(dimethoxyphosphoryl)benzene, subject to the provisos that: when x is 2 or greater, each L may be the same as or different from the other L; and when the precursor compound is a .beta.-diketonate compound of formula (i), L is not phosphate or phosphine oxide. The precursor composition may be employed for forming a lanthanide metal/phosphorus oxide film on a substrate, by depositing a lanthanide metal/phosphorus material on the substrate from the lanthanide metal/phosphorus precursor composition in vaporized form, and incorporating oxygen in the lanthanide metal/phosphorus material to form the lanthanide metal/phosphorus oxide film on the substrate.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to transition metal/phosphorus 
precursor-compounds and compositions for metalorganic chemical vapor 
deposition formation of lanthanide metal/phosphorus oxide films, and to 
composites, devices, and other structures comprising such films, as well 
as methods of making and using such compounds and compositions. 
2. Description of the Related Art 
The implementation of ceramic matrix composites has not significantly 
occurred in turbine engines or power generation systems due to the lack of 
proper coatings for the reinforcement fibers and the absence of a 
commercially useful method to deposit them. Lanthanum phosphate 
(LaPO.sub.4) has arisen as an interface thin film material which could 
provide the characteristics needed for composites to perform as required. 
In addition, thin films of metal phosphates have a wide variety of other 
unrelated applications. Although the art has evolved means to deposit high 
quality coatings, suitable precursors for MOCVD of LaPO.sub.4 are not 
available. Applications of thin film metal phosphates include power 
generation systems, aircraft engines and hazardous waste incinerators. The 
economic reward of using such thin film metal phosphate coatings 
approaches $4 Billion/year in potential energy savings and 0.5 million 
tons of annual NO.sub.x reduction in industrial air emissions. 
Research in fiber/matrix interfaces has successfully demonstrated enhanced 
brittle composite toughness for weak, compliant, sliding, or debonding 
fiber coatings. However, established coatings will not endure the high 
temperature applications without oxidizing or reacting with, and degrading 
properties of, the fiber and/or matrix. The present lack of interfacial 
films with the appropriate debonding/sliding behavior and a high degree of 
mechanical and environmental stability, is a major obstacle in the 
development of composites which will meet design requirements. Several 
researchers have used theoretical modeling to identify candidate interface 
coatings. 
One coating which has shown tremendous promise is LaPO.sub.4. Coatings of 
lanthanum-phosphorus-oxide have been demonstrated via metalorganic 
chemical vapor deposition (MOCVD), and fundamental experiments have 
supported this modeling. However, fiber coating technology, required for 
sample preparation and testing, has not kept pace with these efforts. 
Development efforts have suffered from: (i) a lack of data for precursors 
of metals and nonmetals, (ii) difficulties in applying high quality 
coatings, particularly to continuous multifilament fiber tows, and (iii) 
the high costs associated with the limited fiber coatings that have been 
available. 
An established competitive process for applying fiber coatings is to employ 
sol-gel formation of such coatings. Ceramic fibers are dipped in a bath of 
a solution containing the coating precursors, removed and treated to gel 
the coating. The precursors are then pyrolyzed to form the desired 
coating. Although such a process has a potential advantage of higher 
throughput than MOCVD, coating thickness is low, requiring multiple 
coating runs. Also, bonding of filaments to each other is frequent and 
very difficult to control, and coating texture tends to be very rough and 
powdery which makes the coated fiber difficult to handle. Lastly, coating 
uniformity over the fiber bundle may be poor, leading to weakened sites. 
LaPO.sub.4 also has been proposed as a coating on sapphire fibers in 
polycrystalline Al.sub.2 O.sub.3 matrixes by dipping in a 
slurry/dispersion of LaPO.sub.4 in alcohol solution and firing at 
1400.degree. C. for 1 hr. The ceramic phosphate coating (monazites) form a 
weak bonding interlayer with the ceramic fiber. The interphase material 
allows debonding and frictional sliding between the constituents of the 
composites, inhibits crack growth across the interface, and the composites 
are morphologically stable to high temperature oxidizing environments. 
However, as a result of the inability to control thickness, this method is 
not appropriate for applying LaPO.sub.4 coatings to fibers for production 
scale processing. 
The deposition of metal phosphate thin films has received little attention 
in the open literature. Noncrystalline chromium, molybdenum and tungsten 
phosphates have been deposited using the low valent, phosphine adducts 
M(CO).sub.5 (PH.sub.3). However, the scarcity of known phosphine adducts 
of lanthanide metals renders this methodology of limited use. In addition, 
the toxicity and pyrophoric nature of phosphine discourages 
commercialization of a process based on this class of precursors. The 
safer phosphorus-containing precursor trialkylphosphate OP(OMe).sub.3 has 
been used for the CVD of phosphate glasses, such as phosphosilicates and 
boron phosphate BPO.sub.4. 
Trialkylphosphates and .beta.-diketonate metal complexes have also been 
used to deposit transition metal phosphates. Aerosol CVD has been used to 
deposit phosphate films from (i) Zr(acac).sub.4 (acac=MeC(O)CHC(O)Me) and 
OP(OPh).sub.3, and (ii) Ga(acac).sub.3 and OP(OBu).sub.3. LaPO.sub.4 films 
have been formed on sapphire fibers by coating with a dispersion in 
alcohol and then embedding in an .alpha.-Al.sub.2 O.sub.3 matrix and 
firing at 1400.degree. C. 
A variety of phosphines and their oxidation products exist, including: 
phosphates OP(OR).sub.3, phosphites P(OR).sub.3, phosphine oxides 
OPR.sub.3 and phosphines PR.sub.3. The adducts La(thd).sub.3 OP(OR).sub.3 
!.sub.x and La(thd).sub.3 OPR.sub.3 !.sub.x (PR.sub.3 =PMe.sub.3, 
PMe.sub.2 Bu, Pbu.sub.3) and OP(octyl).sub.3 complex fall apart into its 
separate components with ease, making the CVD process very dependent on 
the deposition parameters. However, only a few percent of phosphorus is 
incorporated when using phosphine oxide adducts. Phosphine oxide adducts 
are also known for fluorinated lanthanum .beta.-diketonates, for instance: 
La(hfac).sub.3 (OPR.sub.3).sub.2. CVD processes utilizing such phosphine 
oxide adducts are also very dependent on the deposition parameters. While 
this dependence could be considered to add flexibility, it also makes 
process reproducibility much more difficult. 
The incorporation of lanthanum into thin films has received growing 
attention due to its use in Pb.sub.1-x La.sub.x TiO.sub.3 (PLT) and 
Pb.sub.1-x La.sub.x (Zr.sub.1-y Ti.sub.y)O.sub.3 (PLZT) ferroelectrics, 
La.sub.2-x M.sub.x CuO.sub.4 (M=Ca, Sr, Ba; x&lt;0.5) high temperature 
superconductors (HTSC), LaCuO.sub.2 piezoelectrics, LaAlO.sub.3 buffer 
layers and La.sub.1-x Ca.sub.x MnO.sub.3 collosal magnetoresistance (CMR) 
materials. Sputtering and pulsed laser deposition of lanthanum 
oxide-containing films have been pursued, but are not suitable techniques 
for the coating of fibers. Materials that have been used for MOCVD growth 
of lanthanum oxide-containing materials include La(.eta.-C.sub.5 H.sub.4 
R).sub.3 (R=H, Me, CHMe.sub.2), and La(thd).sub.3 
(thd=2,2,6,6-tetramethyl-3,5-heptanedionate). La(thd).sub.3 is one of the 
most commonly used precursors; however, process reproducibility is 
difficult since it is a solid precursor often supplied as a hydrated 
material which changes composition with time in the delivery bubbler. 
Process reproducibility is also complicated by any impurity in the source 
reagent, so that the reagent should be of high purity for optimal results. 
The reported melting point of La(thd).sub.3 spans 222.degree.-229.degree. 
C.; however, a closer examination by thermogravimetric 
analysis/differential scanning calorimetry (TGA/DSC) has shown that 
anhydrous material actually undergoes a solid-solid phase transition at 
193.degree. C. and melts at 262.degree. C. and does not vaporize until 
240.degree.-315.degree. C. at atmospheric pressure. The use of TGA/DSC has 
yielded evidence that conversion of La(thd).sub.3 to the oxide is a 
feasible process. In an oxygen atmosphere, thermal oxidation yields 
La.sub.2 O.sub.3 cleanly. 
SUMMARY OF THE INVENTION 
The present invention relates to compositions and methods for forming 
lanthanide metal/phosphorus oxide films (e.g., LaPO.sub.4) on substrates. 
In one compositional aspect of the invention, there is provided a precursor 
composition useful for vapor deposition formation of lanthanide 
metal/phosphorus oxide films, comprising a precursor compound selected 
from the group consisting of: 
(i) adducts of the formula MCp.sub.3 (L).sub.x ; 
(ii) phosphido complexes of the formula M(PR.sub.3).sub.3 or 
M(PR.sub.3).sub.3 L.sub.x ; and 
(iii) disubstituted phosphate complexes of the formulae A.sub.2 M(O.sub.2 
P(OR).sub.2), AM(O.sub.2 P(OR).sub.2).sub.2, and M(O.sub.2 
P(OR).sub.2).sub.3, 
wherein: 
x is from 1 to 5, 
A=Cp or .beta.-diketonate; 
M=a lanthanide metal; 
Cp=cyclopentadienyl, or substituted cyclopentadienyl, 
R=C.sub.1 -C.sub.8 alkyl, and 
L=a phosphorus-containing ligand selected from the group consisting of 
phosphine, phosphine oxide, phosphite, phosphate, and 
1,2-bis(dimethoxyphosphoryl)benzene, 
subject to the provisos that: 
when x is 2 or greater, each L may be the same as or different from the 
other L; and 
when the precursor compound is a .beta.-diketonate compound of formula (i), 
L is not phosphate or phosphine oxide. 
The substituted cyclopentadienyl ligand may comprise as the substituent(s) 
thereof alkyl substituent, e.g., a C.sub.1 -C.sub.4 alkyl moiety, or a 
substituted or unsubstituted silyl moiety. Two illustrative substituted Cp 
ligands are trimethylsilylcyclopentadienyl and methylcyclopentadienyl. 
The precursor composition described above may further comprise a solvent 
for the precursor compound, e.g., a solvent such as tetrahydrofuran, butyl 
acetate, tetraglyme, diethylene triamine, or mixtures thereof, with the 
proviso that the solvent does not contain tetraglyme when L is phosphine. 
In another aspect, the invention relates to a method of forming a 
lanthanide metal/phosphorus oxide film on a substrate, comprising 
depositing a lanthanide metal/phosphorus material on the substrate from a 
vapor-phase lanthanide metal/phosphorus precursor composition comprising a 
precursor compound selected from the group consisting of: 
(i) adducts of the formula MCp.sub.3 (L).sub.x ; 
(ii) phosphido complexes of the formula M(PR.sub.3).sub.3 or 
M(PR.sub.3).sub.3 L.sub.x ; and 
(iii) disubstituted phosphate complexes of the formulae A.sub.2 M(O.sub.2 
P(OR).sub.2), AM(O.sub.2 P(OR).sub.2).sub.2, and M(O.sub.2 
P(OR).sub.2).sub.3, 
wherein: 
x is from 1 to 5, 
A=Cp or .beta.-diketonate; 
M=a lanthanide metal; 
Cp=cyclopentadienyl, or substituted cyclopentadienyl, 
R=C.sub.1 -C.sub.8 alkyl, and 
L=a phosphorus-containing ligand selected from the group consisting of 
phosphine, phosphine oxide, phosphite, phosphate, and 
1,2-bis(dimethoxyphosphoryl)benzene, 
subject to the provisos that: 
when x is 2 or greater, each L may be the same as or different from the 
other L; and 
when the precursor compound is a .beta.-diketonate compound of formula (i), 
L is not phosphate or phosphine oxide; and 
incorporating oxygen in the lanthanide metal/phosphorus material to form 
the lanthanide metal/phosphorus oxide film on the substrate. 
In such method, the step of depositing a lanthanide metal/phosphorus 
material on the substrate from a vapor-phase lanthanide metal/phosphorus 
precursor composition preferably comprises chemical vapor deposition of 
said lanthanide metal/phosphorus material from said precursor composition. 
The step of incorporating oxygen in the lanthanide metal/phosphorus 
material to form the lanthanide metal/phosphorus oxide film on the 
substrate, may be carried out by exposing the deposited lanthanide 
metal/phosphorus material to an oxygen-containing gas subsequent to 
deposition of the lanthanide metal/phosphorus material, or alternatively 
by depositing said material on the substrate in an oxygen-containing 
environment. For example, in the substrate environment, oxygen may be 
present in the form of N.sub.2 O or oxygen may be present in a precursor 
ligand species in such environment. 
Other aspects and features of the invention will be more fully apparent 
from the ensuing disclosure and appended claims.

DETAILED DESCRIPTION OF THE INVENTION, AND PREFERRED EMBODIMENTS THEREOF 
The compositions of the invention include a precursor compound selected 
from the group consisting of: 
(i) adducts of the formula MCp.sub.3 (L).sub.x ; 
(ii) phosphido complexes of the formula M(PR.sub.3).sub.3 or 
M(PR.sub.3).sub.3 L.sub.x ; and 
(iii) disubstituted phosphate complexes of the formulae A.sub.2 M(O.sub.2 
P(OR).sub.2), AM(O.sub.2 P(OR).sub.2).sub.2, and M(O.sub.2 
P(OR).sub.2).sub.3, 
wherein: 
x is from 1 to 5, 
A=Cp or .beta.-diketonate; 
M=a lanthanide metal; 
Cp=cyclopentadienyl, or substituted cyclopentadienyl, 
R=C.sub.1 -C.sub.8 alkyl, and 
L=a phosphorus-containing ligand selected from the group consisting of 
phosphine, phosphine oxide, phosphite, phosphate, and 
1,2-bis(dimethoxyphosphoryl)benzene, 
subject to the provisos that: 
when x is 2 or greater, each L may be the same as or different from the 
other L; and 
when the precursor compound is a .beta.-diketonate compound of formula (i), 
L is not phosphate or phosphine oxide. 
Each of these precursor compounds is described in turn below. As used 
herein, the term "lanthanide metal" encompasses the metals of the 
lanthanide series of the Periodic Table, including the following metal 
species: La, Ce, Y, Nd, Pr, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and 
Lu. 
Lanthanide Metal Cp Adducts 
The adducts of the lanthanide metal .beta.-diketonates or cyclopentadienyls 
can be prepared by addition of one or two equivalents of the desired 
ligand to either La(thd).sub.3, in accordance with reaction (1a) below, or 
alternatively to MCp.sub.3 in accordance with reaction (1b) below. 
EQU M(thd).sub.3 +xL.fwdarw.M(thd).sub.3 (L)x (1a) 
EQU MCp.sub.3 +xL.fwdarw.MCp.sub.3 (L)x (1b) 
Table I below sets out some phosphorus-containing ligands L for M(Cp).sub.3 
(L).sub.x. 
TABLE 1 
______________________________________ 
Phosphorus-containing ligands L for M(thd/Cp).sub.3 (L).sub.x 
Ligand L Formula Structure 
______________________________________ 
Monodentate Phosphines 
PR.sub.3 
##STR1## 
Bidentate Phosphines 
R.sub.2 PCH.sub.2 CH.sub.2 PR.sub.2 
##STR2## 
Phosphates OP(OR).sub.3 
##STR3## 
Phosphine oxides 
OPR.sub.3 
##STR4## 
Phosphites P(OR).sub.3 
##STR5## 
1,2-Bis(dimethoxy- phosphoryl)-benzene 
C.sub.6 H.sub.4 PO(OMe).sub.2 !.sub.2 
##STR6## 
In contrast to phosphine oxide OPR.sub.3 and phosphate OP(OR).sub.3 
.beta.-diketonate adducts, there is some evidence that LaCp.sub.3 adducts 
may be oligomeric in structure. Illustrative examples of the ligands 
tabulated in Table 1 include monodentate phosphines such as 
P(n-Bu).sub.3, bidentate phosphines such as Me.sub.2 PCH.sub.2 CH.sub.2 
PMe.sub.2, and phosphites such as P(OMe).sub.3. These ligands and the 
potentially chelating 1,2-bis(dimethoxy-phosphoryl)benzene C.sub.6 
H.sub.4 PO(OMe).sub.2 !.sub.2 ligand may be usefully employed with 
MCp.sub.3 centers (coordinating moieties). The 1,2-bis(dimethoxy-phosphory 
l)benzene ligand has a structurally rigid phenyl backbone for preventing 
facile dissociation of the ligand thereby enhancing phosphorus 
Lanthanide Metal Phosphido Complexes 
Direct incorporation of the phosphorus in the coordinated complex, in a 
form less susceptible to dissociation, may substantially increase the 
incorporation of phosphorus in the deposited lanthanide metal/phosphorus 
material. Materials such as La(PR.sub.2).sub.3 may be dimeric or Lewis 
base adducts. Homoleptic dialkylphosphido complexes are known for 
virtually every transition metal and include the following lanthanide 
species: Ln(P(SiMe.sub.3).sub.2).sub.3 (thf).sub.2 (Ln=Tm, Nd) and 
Ln(PPh.sub.2).sub.2 (thf).sub.4 (Ln=Sm, Yb). The only reported lanthanum 
diphosphide of which we are aware is the structurally characterized 
LaP(2-C.sub.6 H.sub.4 OMe).sub.2 !.sub.3. 
Oxidation of M(PR.sub.2).sub.3 may be employed to yield lanthanide metal 
phosphates such as LaPO.sub.4. Excess phosphorus may be extruded as 
P.sub.2 R.sub.4, a common thermolysis by-product. 
The phosphido complexes may be formed in a manner analogous to the 
synthesis of the related lanthanide alkoxide Ln(OR).sub.3 complexes. The 
most basic reaction is the salt metathesis reaction using anhydrous 
LaCl.sub.3 !.sub.x which is commercially available and LiPR.sub.2 as 
shown in reaction (2a) below. Occasionally problems with lanthanides arise 
due to the formation of mixed metal salt complexes. In these cases either 
the byproduct LiCl or excess starting material LiPR.sub.2 coordinates to 
the desired product to yield materials such as LiLa(PR.sub.2).sub.3 Cl! 
or LiLa(PR.sub.2).sub.4 !. This problem often can be solved by the 
reacting LaI3(thf).sub.x with potassium salts of the desired phosphide 
KPR.sub.2 as shown in reaction (2b) below. The greater solubility of the 
iodide salt LaI.sub.3 (thf).sub.x over anhydrous LaCl.sub.3 !.sub.x 
allows for more rapid completion of reactions, while the covalent nature 
of KI renders it less likely than the ionic LiCl to complex with the 
desired product. An alternative method to avoid complex mixed metal salts 
is the displacement of amine reactions from elimination amides such as 
La(N(SiMe.sub.3).sub.2).sub.3 or La(N-iPr.sub.2).sub.3 (thf) as shown in 
reaction 2c below. 
##STR7## 
Disubstituted Phosphate Complexes L.sub.x MO.sub.2 P(OR).sub.2 !.sub.3-x 
Much of the problem with previously reported approaches to incorporation of 
phosphorus in La-P-O films relates to the facile loss of the neutral 
phosphine ligand. Synthesis of phosphides may be complicated by the 
material's sensitivity to air and moisture, problems which are overcome by 
utilization of ligands containing both oxygen and phosphorus, in the 
disubstituted phosphate complexes of the formula L.sub.x MO.sub.2 
P(OR).sub.2 !.sub.3-x. 
These disubstituted phosphate complexes may be formed by reaction of 
(R).sub.2 PO(OH) where R is alkyl, e.g., i-butyl, propyl, or aminoalkenyl, 
with lanthanide metal compounds such as LaO.sub.2 P(t-Bu).sub.2 !.sub.3, 
A.sub.2 LaO.sub.2 P(t-Bu).sub.2 ! and ALaO.sub.2 P(t-Bu).sub.2 !.sub.2, 
where A=Cp or .beta.-diketonate. 
The precursor composition described above may further comprise a solvent 
for the precursor compound, e.g., a solvent such as tetrahydrofuran, butyl 
acetate, tetraglyme, diethylene triamines, or mixtures thereof, with the 
proviso that the solvent does not contain tetraglyme when L is phosphine. 
Examples of solvent formulations which may be usefully employed include 
mixtures of tetrahydrofuran and tetraglyme, e.g., in a 9:1 ratio by 
weight. 
In the precursors of the invention comprising a phosphine moiety as the 
phosphorus-containing ligand thereof, the phosphine may be monodentate or 
bidentate in character. In general, the compounds of the invention may be 
employed to provide a desired stoichiometric ratio of lanthanide 
metal:phosphorus, e.g., 1:1, 1:2, or 2:1, by selection of an appropriate 
compound or compounds from among the group comprising: (i) adducts of the 
formula MA.sub.3 (L).sub.x ; (ii) phosphido complexes of the formula 
M(PR.sub.3).sub.3 or M(PR.sub.3).sub.3 L.sub.x ; and (iii) disubstituted 
phosphate complexes of the formula A.sub.2 M(O.sub.2 P(OR).sub.2, 
AM(O.sub.2 P(OR).sub.2).sub.2, and M(O.sub.2 P(OR).sub.2).sub.3. 
The organo substituents R of the lanthanide metal/phosphorus precursors of 
the invention include C.sub.1 -C.sub.8 alkyl, preferably C.sub.1 -C.sub.4 
alkyl, as well as other suitable hydrocarbyl groups. 
The precursor compositions of the invention may be usefully employed in 
forming a lanthanide metal/phosphorus oxide film on a substrate, by 
depositing a lanthanide metal/phosphorus material on the substrate from a 
vapor-phase lanthanide metal/phosphorus precursor composition of the 
invention, and oxidizing the lanthanide metal/phosphorus material to form 
the lanthanide metal/phosphorus oxide film on the substrate. The 
deposition may comprise any suitable type of chemical vapor deposition 
(CVD), including low pressure CVD and/or assisted CVD techniques (e.g., 
plasma, laser, etc.), atmospheric pressure CVD, etc., on any appropriate 
substrate. 
The lanthanide metal/phosphorus precursor composition of the invention may 
be utilized in solid form as a single source solid reagent, in a bubbler 
or other suitable device for forming a source vapor for the deposition of 
the lanthanide metal/phosphorus material. Alternatively, the lanthanide 
metal/phosphorus precursor composition may be dissolved in any suitable 
solvent and vaporized for passage to the CVD reactor or other deposition 
locus, using a liquid delivery and vaporization system, such as that 
disclosed in Kirlin et al. U.S. Pat. No. 5,536,323 issued Jul. 16, 1996, 
the disclosure of which is hereby incorporated herein in its entirety. 
In the method of the invention, the step of oxidizing the lanthanide 
metal/phosphorus material to form the lanthanide metal/phosphorus oxide 
film on the substrate, may be carried out by exposing the deposited 
lanthanide metal/phosphorus material to an oxygen-containing gas, such as 
pure oxygen, N.sub.2 O, or an oxygen/inert gas mixture, subsequent to 
deposition of the lanthanum/phosphorus material, or alteratively by 
depositing such material on the substrate in an oxygen-containing 
environment. Oxygen may be furnished in the deposition environment by the 
solvent used as a carrier medium for the precursor, or the precursor 
composition itself may contain the requisite oxygen for the formation of 
an oxide film. The present invention may employ any of such modes of 
incorporating oxygen in the deposited lanthanum/phosphorus material. The 
deposition and oxygen-incorporation steps may be carried out at any 
suitable process conditions, as may be readily determined without undue 
experimentation by those skilled in the art. 
In a particularly preferred end use application, the precursor composition 
and method of the invention may be employed to manufacture high 
performance ceramic composites, by forming a lanthanide metal phosphate 
coating on fiber or other discontinuous reinforcement media, e.g., of 
sapphire or other glass, metal, or ceramic medium, which is subsequently 
incorporated in a composite matrix material whose continuous phase 
comprises a high performance ceramic or cermet material. 
While the invention has been described herein with reference to specific 
illustrative aspects and embodiments thereof, it will be appreciated that 
the utility of the invention is not thus limited, but rather extends to 
variations, modifications and other embodiments of the specifically 
disclosed features. 
For example, although the invention has been described most specifically in 
reference to the deposition of lanthanum/phosphorus films, it will be 
appreciated that the invention may also be practiced with other lanthanide 
metals than lanthanum per se. 
The invention is therefore to be correspondingly broadly construed and 
interpreted, as encompassing within its scope all such variations, 
modifications and embodiments.