Abstract:
The present invention relates to a ceramic dielectrics. It is difficult to downsize a MgTiO 2  -base ceramic composition conventionally used, having an insufficiently high relative dielectric constant (.di-elect cons. r ), less than 20, while a CaTiO 3  -base ceramic composition, having a small value of Q, is not suitable for electronic devices processing a signal in the high-frequency-bandwidth. Moreover, it is difficult to control the temperature coefficient of resonant frequency of these conventional ceramic compositions. In the present invention, a ceramic dielectrics having a composition represented by xMgTiO 3 .(1-x)CaTiO 3 .y(Ln 1   1-w  Ln 2   w ) 2  Ti 2z  O 3+4z  (wherein Ln 1  and Ln 2  are lanthanoids, and w, x, y, and z are values in the ranges of 0≦w&lt;1, 0.20≦x≦0.80, 0.05≦y≦5.0, and 0.25≦z≦1.5, respectively) contributes to solving the above problems. The ceramic dielectrics according to the present invention can be used as a material for a resonator processing a signal in the microwave-bandwidth, a filter, a capacitor or the like.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a ceramic dielectrics and a method for forming the same. 
     DESCRIPTION OF THE PRIOR ART 
     Recently, ceramic dielectrics for high frequency signals have been widely utilized as a material for a resonator used in an antenna duplexer of radio communication equipments such as a mobile phone, a cellular phone and a cordless telephone, a voltage-controlled oscillator (VCO) etc., or a filter used in a tuner for CATV. By using a material having a high dielectric constant for these applications, the wave length of an electromagnetic wave can be shortened to the length of .di-elect cons. r   -1/2  (.di-elect cons. r  : relative dielectric constant) under vacuum, so that one wave length, half a wave length or a quarter of a wave length, a resonant condition of an electromagnetic wave, can be shortened. Therefore, when the material is used, electronic devices which process electric signals using a resonance of an electromagnetic wave can be easily downsized. 
     Characteristics required for the ceramic dielectrics for high frequency signals are: 
     (1) Since the wave length of an electromagnetic wave is shortened to .di-elect cons. r   -1/2  in dielectrics, among ceramic dielectrics having the same resonant frequency, those which have a higher dielectric constant can be more downsized. Thus, the dielectric constant should be as high as possible; 
     (2) The dielectric loss (1/Q) should be small in the high-frequency-bandwidth, that is, the value of Q should be large; and 
     (3) The variation of a resonant frequency depending on a temperature variation should be small, that is, the dependency on temperature of the relative dielectric constant (.di-elect cons. r ) should be small. 
     Besides, a reference clock frequency of electronic devices has been chosen in the microwave-bandwidth in many cases, and at present, the clock frequency of electronic equipment for the consumer is 1 GHz or so. However, as an increase of information content delivered per unit time, and a controlling speed of electronic equipment and a processing speed of signals have become faster, electronic devices for a microwave which can be also used in a higher-frequency-bandwidth (several GHz) are becoming necessary. Accordingly, as a ceramic dielectrics constituting the electronic devices for a microwave, a material having a large value of Q is required to make a microwave loss as small as possible. In addition, a material having a high dielectric constant is required to make the electronic devices as small as possible. 
     Hitherto, as ceramic dielectrics having the above characteristics, a MgTiO 3  -base and a CaTiO 3  -base ceramic dielectrics have been known. 
     The conventional MgTiO 3  -base ceramic dielectrics has a large value of Q, but has a relative dielectric constant (.di-elect cons. r ) of less than 20, which is not sufficiently high. As a result, it is difficult to downsize an element with the MgTiO 3  -base ceramic dielectrics therein. On the other hand, the CaTiO 3  -base ceramic dielectrics has a high dielectric constant, but has a small value of Q. As a result, it is not suitable for electronic devices processing signals in the high-frequency-bandwidth, and it is not suitable for being put to practical use because of its extremely high temperature coefficient of resonant frequency (τ f ). 
     Moreover, since it is difficult to control the temperature coefficient of resonant frequency (τ f ) without changing the composition of these materials, it is required to change the temperature coefficient of resonant frequency (τ f ) by adding several kinds of additives such as rare earth elements to the above materials. But a ceramic dielectrics available for several requirements cannot be easily provided since the characteristics in changing compositions have not been systematically examined. 
     DISCLOSURE OF THE INVENTION 
     The present invention was achieved in order to solve these problems, and it is an object to provide a ceramic dielectrics having a larger value of Q and a higher relative dielectric constant (.di-elect cons. r ) than ever, whose temperature coefficient of resonant frequency (τ f ) can be controlled to an optional value in the range of +100 to -100 ppm/°C., and a method for forming the same. 
     A ceramic dielectrics (1) according to the present invention have a composition represented by xMgTiO 3 .(1-x)CaTiO 3 .y(Ln 1   1-w  Ln 2   w ) 2  Ti 2z  O 3+4z  (wherein Ln 1  and Ln 2  are lanthanoids, and w, x, y, and z are values in the ranges of 0≦w&lt;1, 0.20≦x≦0.80, 0.05≦y≦5.0 and 0.25≦z≦1.5, respectively.). 
     A ceramic dielectrics (2) according to the present invention substantially comprise a composition as a principal component represented by xMgTiO 3 .(1-x)CaTiO 3 .y(Ln 1   1-w  Ln 2   w ) 2  Ti 2z  O 3+4z  (wherein Ln 1  and Ln 2  are lanthanoids, and w, x, y, and z are values in the ranges of 0≦w&lt;1, 0.20≦x≦0.80, 0.05≦y≦5.0 and 0.25≦z≦1.5, respectively.) and ZnO and/or MnO as additives in the range of a mol (where, 0&lt;a≦0.2) to 1 mol of the principal component. 
     A ceramic dielectrics (3) according to the present invention have a composition represented by xMgTiO 3 .(1-x)CaTiO 3 .y(Nd 1-w  Ln 2   w ) 2  Ti 2z  O 3+4z  (wherein Ln 2  is a lanthanoid, and w, x, y, and z are values in the ranges of 0≦w&lt;1, 0.20≦x≦0.80, 0.05≦y≦5.0 and 0.25≦z≦1.5, respectively.). 
     A ceramic dielectrics (4) according to the present invention substantially comprise a composition as a principal component represented by xMgTiO 3 .(1-x)CaTiO 3 .y(Nd 1-w  Ln 2   w ) 2  Ti 2z  O 3+4z  (wherein Ln 2  is a lanthanoid, and w, x, y, and z are values in the ranges of 0≦w&lt;1, 0.20≦x≦0.80, 0.05≦y≦5.0 and 0.25≦z≦1.5, respectively.) and ZnO and/or MnO as additives, in the range of a mol (where, 0&lt;a≦0.2) to 1 mol of the principal component. 
     The above ceramic dielectrics (1)-(4) have a high relative dielectric constant (.di-elect cons. r ), 30-70, and a small dielectric loss because of a high value of Q, 3000 or more at a measuring frequency of 3 GHz, and by changing their compositions and so on, their temperature coefficient of resonant frequency (τ f ) can be controlled to a particular value in the range of +100 to -100 ppm/°C. 
     Besides, by making use of the electric characteristics of these ceramic dielectrics (1)-(4), a resonator for high frequency signals, a filter etc. can be sharply downsized. 
     A method for forming a ceramic dielectrics (1) according to the present invention comprises the steps of preparing raw materials selected from compounds each of which contains one of Mg, Ca, Ti, Ln 1 , and Ln 2  (here, Ln 1  and Ln 2  are lanthanoids) in such a proportion as a ceramic composition represented by xMgTiO 3 .(1-x)CaTiO 3 .y(Ln 1   1-w  Ln 2   w ) 2  Ti 2z  O 3+4z  (wherein Ln 1  and Ln 2  are lanthanoids, and w, x, y, and z are values in the ranges of 0≦w&lt;1, 0.20≦x≦0.80, 0.05≦y≦5.0 and 0.25≦z≦1.5, respectively.) is formed after being sintered, mixing, pressing, and then sintering the same at a temperature of 1200°-1600° C. in the air or an oxygen atmosphere. 
     A method for forming a ceramic dielectrics (2) according to the present invention comprises the steps of preparing raw materials selected from compounds each of which contains one of Mg, Ca, Ti, Ln 1 , and Ln 2  (here, Ln 1  and Ln 2  are lanthanoids) and a powder as sintering agents selected from compounds containing Zn and/or Mn in such a proportion as a ceramic composition substantially comprising a composition as a principal component represented by xMgTiO 3 .(1-x)CaTiO 3 .y(Ln 1   1-w  Ln 2   w ) 2  Ti 2z  O 3+4z  (wherein Ln 1  and Ln 2  are lanthanoids, and w, x, y, and z are values in the ranges of 0≦w&lt;1, 0.20≦x≦0.80, 0.05≦y≦5.0 and 0.25≦z≦1.5, respectively.) and ZnO and/or MnO as additives in the range of a mol (where, 0&lt;a≦0.2) to 1 mol of the principal component is formed after being sintered, mixing, pressing, and then sintering the same at a temperature of 1200°-1600° C. in the air or an oxygen atmosphere. 
     A method for forming a ceramic dielectrics (3) according to the present invention comprises the steps of preparing raw materials selected from compounds each of which contains one of Mg, Ca, Ti, Ln 1 , and Ln 2  (here, Ln 1  and Ln 2  are lanthanoids) in such a proportion as a ceramic composition represented by xMgTiO 3 .(1-x)CaTiO 3 .y(Ln 1   1-w  Ln 2   w ) 2  Ti 2z  O 3+4z  (wherein Ln 1  and Ln 2  are lanthanoids, and w, x, y, and z are values in the ranges of 0≦w&lt;1, 0.20≦x≦0.80, 0.05≦y≦5.0 and 0.25≦z≦1.5, respectively.) is formed after being sintered, mixing, calcining, granulating, pressing, and then sintering the same at a temperature of 1200°-1600° C. in the air or an oxygen atmosphere. 
     A method for forming a ceramic dielectrics (4) according to the present invention comprises the steps of preparing raw materials selected from compounds each of which contains one of Mg, Ca, Ti, Ln 1 , and Ln 2  (here, Ln 1  and Ln 2  are lanthanoids) and a powder as sintering agents selected from compounds containing Zn and/or Mn in such a proportion as a ceramic composition substantially comprising a composition as a principal component represented by xMgTiO 3 .(1-x)CaTiO 3 . y(Ln 1   1-w  Ln 2   w ) 2  Ti 2z  O 3+4z  (wherein Ln 1  and Ln 2  are lanthanoids, and w, x, y, and z are values in the ranges of 0≦w&lt;1, 0.20≦x≦0.80, 0.05≦y≦5.0 and 0.25≦z≦1.5, respectively.) and ZnO and/or MnO as additives in the range of a mol (where, 0&lt;a≦0.2) to 1 mol of the principal component is formed after being sintered, mixing, calcining, granulating, pressing, and then sintering the same at a temperature of 1200°-1600° C. in the air or an oxygen atmosphere. 
     A method for forming ceramic dielectrics (5) according to the present invention comprises the steps of preparing raw materials selected from compounds each of which contains one of Mg, Ca, Ti, Nd, and Ln 2  (here, Ln 2  is a lanthanoid) in such a proportion as a ceramic composition represented by xMgTiO 3 .(1-x)CaTiO 3 . y(Nd 1-w  Ln 2   w ) 2  Ti 2z  O 3+4z  (wherein Ln 2  is a lanthanoid, and w, x, y, and z are values in the ranges of 0≦w&lt;1, 0.20≦x≦0.80, 0.05≦y≦5.0 and 0.25≦z≦1.5, respectively.) is formed after being sintered, mixing, calcining, granulating, pressing, and then sintering the same at a temperature of 1200°-1600° C. in the air or an oxygen atmosphere. 
     A method for forming a ceramic dielectrics (6) according to the present invention comprises the steps of preparing raw materials selected from compounds each of which contains one of Mg, Ca, Ti, Nd, and Ln 2  (here, Ln 2  is a lanthanoid) and a powder as sintering agents selected from compounds containing Zn and/or Mn in such a proportion as a ceramic composition substantially comprising a composition as a principal component represented by xMgTiO 3 .(1-x)CaTiO 3 . y(Nd 1-w  Ln 2   w ) 2  Ti 2z  O 3+4z  (wherein Ln 2  is a lanthanoid, and w, x, y, and z are values in the ranges of 0≦w&lt;1, 0.20≦x≦0.80, 0.05≦y≦5.0 and 0.25≦z≦1.5, respectively.) and ZnO and/or MnO as additives in the range of a mol (where, 0&lt;a≦0.2) to 1 mol of the principal component is formed after being sintered, mixing, calcining, granulating, pressing, and then sintering the same at a temperature of 1200°-1600° C. in the air or an oxygen atmosphere. 
     According to the above methods for forming a ceramic dielectrics (1)-(6), a sintered body can have a uniform grain size and a ceramic dielectrics having a high relative dielectric constant (.di-elect cons. r ), 30-70, and a small dielectric loss because of a high value of Q, 3000 or more at a measuring frequency of 3 GHz, whose temperature coefficient of resonant frequency (τ f ) can be controlled to a particular value in the range of +100 to -100 ppm/°C. by changing their compositions etc., can be easily manufactured. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1(a) is a diagrammatic plain figure showing an apparatus used for measuring electric characteristics of the ceramic dielectrics according to Examples in the present invention, and FIG. 1(b) is a front view thereof. 
    
    
     FORM FOR CONDUCTING THE INVENTION 
     In the above methods for forming a ceramic dielectrics, raw materials are selected from compounds each of which contains one or two of Mg, Ca, Ti, and lanthanoids, and are prepared. In the case where addition of sintering agents is required, a powder selected from compounds containing Zn and Mn is added to the prepared raw materials. The compounds constituting these raw materials are not limited to oxides of the above elements and other compounds are available. For example, raw materials of carbonate, oxalate, nitrate, and alkoxide, which give oxides after being sintered, are exemplified. When oxides or carbonates of the above elements are used as raw materials, the average grain size of these compounds is preferably several μm or so. These raw materials are wet mixed in the usual way, and then dried, calcined, crushed, granulated, pressed and so on, so as to form a pressed body having a prescribed shape. After sintering the same, a ceramic is obtained. 
     To be concrete, every raw material is accurately weighed in the above composition, which is wet mixed with balls, a well-known dispersant and distilled water in a pot mill for 24 hours or so, and finally a raw material mixture in a slurry is obtained. Next, the mixture in a slurry is dried and crushed. Then, the crushed powder may be transferred to a zirconia crucible for sintering, be calcined and synthesized at a temperature of 1000°-1200° C., and be crushed again, depending on necessity. As for the temperature condition of calcination and synthesis, the above range of temperature is preferable, since at a temperature of less than 1000° C., a large amount of raw material is left and uniform sintering is prohibited, while at a temperature of over 1200° C., sintering starts, which makes pulverizing difficult, and in both cases the value of Q tends to decrease. 
     Then, the crushed powder is granulated to a powder having an almost uniform grain size. After an organic binder etc. is added to the granulated powder, a pressed body having a prescribed shape is formed. As another way, a granulation treatment may be conducted by a spray drier etc. on the crushed powder with an organic binder etc. added thereto and a pressed body may be formed from the obtained powder. 
     Then, the ceramic dielectric is obtained by defatting the obtained pressed body at a temperature of 600° C. or so, placing the defatted pressed body on a plate for sintering made of MgO etc., and sintering the pressed body placed thereon at a temperature of 1200°-1600° C. in the air or an oxygen atmosphere for 2-8 hours. When the sintering temperature is less than 1200° C., the pressed body is not sufficiently made fine, its value of Q becomes small, and its relative dielectric constant (.di-elect cons. r ) does not become high, while when the sintering temperature is over 1600° C., the ceramic dielectric itself becomes soft and the shape of the pressed body before being sintered cannot be kept. As a result, the above range of temperature is preferable. 
     The ceramic dielectrics formed by the above method have a high relative dielectric constant (.di-elect cons. r ), 30-70, and a large value of Q, 3000 or more at a measuring frequency of 3 GHz. In addition, it is possible to control its temperature coefficient of resonant frequency (τ f ) to a particular value in the range of +100 to -100 ppm/°C. by changing x, y etc. in the composition formula. And the tissue structure of the ceramic dielectrics has an almost uniform grain size and is extremely fine, having a sintering density of 96.0-100% or so to the theoretical density, and is excellent in mechanical characteristics, so that it is suitable for use for a resonator or the like. 
     In the ceramic dielectrics, Ln 1  and Ln 2  are rare earth lanthanoid elements, and as the elements, La, Ce, Nd, Gd, Sm, and Dy are exemplified. As mentioned before, the temperature coefficient of resonant frequency (τ f ) can be controlled by changing the mixing ratio of these lanthanoids (y). 
     X is an atom ratio of Mg to a total amount of Mg and Ca in the ceramic dielectrics. When x is less than 0.20, Q becomes small, 3000 or less (at 3 GHz), and the temperature coefficient of resonant frequency (τ f ) becomes larger than 100, while when x is over 0.80, the relative dielectric constant (.di-elect cons. r ) becomes small, less than 30. 
     Y is a mol ratio of (Ln 1   1-w  Ln 2   w ) 2  Ti 2z  O 3+4z  to (xMgTiO 3  +(1-x)CaTiO 3 ). When y is less than 0.05, the temperature coefficient of resonant frequency (τ f ) becomes too large, while when y is over 5.0, Q becomes small, 3000 or less. 
     Z is a mol ratio of Ti to lanthanoids. When z is less than 0.25, Q becomes small, 3000 or less, while when z is over 1.5, the temperature coefficient of resonant frequency (τ f ) becomes too large. 
     A is mols of sintering agents to 1 mol of the principal component. The sintering agents contribute to a rise in Q when it is added in the case where sintering is difficult because of a small amount of Ti. On the other hand, the temperature coefficient of resonant frequency (τ f ) becomes small by adding the sintering agents. When a is over 0.20, Q becomes small, 3000 or less. 
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Examples and Comparative Examples of a ceramic dielectric and a method for forming the same according to the present invention are described below. 
     First, a method for forming ceramic dielectrics according to Examples is explained. 
     Raw materials selected from MgO, CaCo 3 , TiO 2 , Ln 1   2  O 3 , and Ln 2   2  O 3  (Ln 1  and Ln 2  are lanthanoids), having an average grain size of some μm, were prepared in the proportions shown in Tables 1-5. Here, w, x, y, 2z, and a in Tables 1-5 correspond to the letters representing the ceramic dielectrics (1) and (2). In addition, as sintering agents, ZnO and MnCO 3  having the same average grain size as them were used. 
     A method for forming a sintered body is as described in the &#34;FORM FOR CONDUCTING THE INVENTION&#34;, and as a raw material for pressing, powder calcined at 1000° C., and then crushed and granulated by addition of an organic binder etc. were used. 
     As for the composition of the ceramic dielectrics obtained by the above sintering, by conducting an ICP emission spectrochemical analysis after the ceramic dielectric was dissolved in an acid, it was confirmed that the composition of the sintered body is the same as the preparation composition of the raw materials. For further observation of the structure of the sintered body, an etching treatment was conducted on the sintered body after being broken, and the surface thereof was observed with a scanning electron microscope (SEM). As a result, it was proved that the ceramic dielectrics according to Examples have a fine structure formed from particles having an almost uniform grain size. 
     And in order for measuring electric characteristics, a sample for the measurement of electric characteristics was formed by sufficiently washing the obtained sintered body in distilled water, and then polishing it into such a shape as it has parallel main surfaces and a resonant frequency of 3 GHz. 
     Next, a method for measuring electric characteristics of the ceramic dielectrics according to Examples is explained. 
     As the electric characteristics, the resonant frequency, relative dielectric constant (.di-elect cons. r ) and Q were measured by the Hakki-Coleman dielectric resonator method. 
     FIG. 1(a) is a plain figure diagrammatically showing an apparatus used for measuring the electric characteristics, and FIG. 1(b) is a front view thereof. 
     A sample (ceramic dielectric) 11, a subject of the measurement, is fixed in the state of being interposed between two parallel metal plates 12. 13 represents a column for keeping the metal plate stable on the sample. 
     In measuring the dielectric constant, the frequency characteristic was measured by oscillating a high frequency from a probe 14 of a network analyzer, and the relative dielectric constant (.di-elect cons. r ) was calculated from the obtained resonant frequency peak in TEO1 δ mode and the dimensions of a sample 11. As for measuring Q, the surface specific resistance of a metal plate 12 was found by using a standard sample, from which the dielectric loss for a metal plate 12 was found, and Q of a sample 11 was calculated by subtracting the dielectric loss for a metal plate 12 from the total dielectric loss. And the temperature coefficient of resonant frequency (τ f ) was measured in the atmospheric temperature range from -30° to +85° C. 
     As the samples for the measurement, fifty samples of every Example (composition) were manufactured and the electric characteristics of each sample 11 were measured, and average values thereof were calculated. The results are shown in Tables 1-5. 
     Here, as Comparative Examples, the electric characteristics of the ceramic dielectrics having a composition outside the range of the present invention, manufactured under the same conditions as Examples, and those of the ceramic dielectrics having a composition within the range of the present invention, manufactured at a sintering temperature of less than 1200° C. or more than 1600° C., were measured. The results are also shown in Tables 1-5. Comparative Examples are marked *. 
     
                                           TABLE 1__________________________________________________________________________                         Relative   Tempera-                    Sintering                         Dielec-    tureComposition of Ceramic Dielectrics                    Tempera-                         tric       Coeffi-Sample Ln.sup.1  Sintering                    ture Constant                              Value of Q                                    cient τ.sup.fNo. x  (w = 0)      y  2z Agent                 a  (°C.)                         (ε.sub.r)                              (at 3 GHz)                                    (ppm/°C.)                                          Note__________________________________________________________________________1   0.900  Nd  0.150         1.000   0.000                    1400 20   50000 -15   *2   0.800  Nd  0.150         1.000   0.000                    1400 32   11000 93   0.700  Nd  0.150         1.000   0.000                    1400 42   8000  184   0.600  Nd  0.150         1.000   0.000                    1400 56   7300  315   0.500  Nd  0.150         1.000   0.000                    1400 62   6500  486   0.400  Nd  0.150         1.000   0.000                    1400 67   6200  567   0.300  Nd  0.150         1.000   0.000                    1400 69   6000  718   0.200  Nd  0.150         1.000   0.000                    1400 70   4700  859   0.100  Nd  0.150         1.000   0.000                    1400 71   1800  101   *10  0.500  Nd  0.000         1.000   0.000                    1400 72   1500  125   *11  0.500  Nd  0.005         1.000   0.000                    1400 69   3200  117   *12  0.500  Nd  0.040         1.000   0.000                    1400 68   1100  111   *13  0.500  Nd  0.050         1.000   0.000                    1400 67   3800  6314  0.500  Nd  0.250         1.000   0.000                    1400 58   6300  4015  0.500  Nd  0.500         1.000   0.000                    1400 52   6000  3716  0.500  Nd  1.000         1.000   0.000                    1400 49   6700  1917  0.500  Nd  1.500         1.000   0.000                    1400 46   6600  618  0.500  Nd  2.500         1.000   0.000                    1400 39   3500  -1019  0.500  Nd  5.000         1.000   0.000                    1400 45   6000  -1520  0.500  Nd  5.300         1.000   0.000                    1400 35   1000  --    *21  0.500  Sm  0.005         1.000   0.000                    1400 63   5700  109   *22  0.500  Sm  0.040         1.000   0.000                    1400 56   2300  105   *23  0.500  Sm  0.050         1.000   0.000                    1400 58   5200  6224  0.500  Sm  0.500         1.000   0.000                    1400 50   5900  3825  0.500  Sm  1.000         1.000   0.000                    1400 47   6200  1826  0.500  Sm  1.500         1.000   0.000                    1400 42   5900  -1527  0.500  Sm  2.500         1.000   0.000                    1400 31   3800  -2428  0.500  Sm  5.000         1.000   0.000                    1400 30   3500  -1529  0.500  Sm  5.300         1.000   0.000                    1400 24   1500  --    *__________________________________________________________________________ 
    
     
                                           TABLE 2__________________________________________________________________________                         Relative   Tempera-                    Sintering                         Dielec-    tureComposition of Ceramic Dielectrics                    Tempera-                         tric       Coeffi-Sample Ln.sup.1  Sintering                    ture Constant                              Value of Q                                    cient τ.sup.fNo. x  (w = 0)      y  2z Agent                 a  (°C.)                         (ε.sub.r)                              (at 3 GHz)                                    (ppm/°C.)                                          Note__________________________________________________________________________30  0.500  Gd  0.005         1.000   0.000                    1400 61   1800  105   *31  0.500  Gd  0.040         1.000   0.000                    1400 60   1500  135   *32  0.500  Gd  0.050         1.000   0.000                    1400 56   4300  6033  0.500  Gd  0.500         1.000   0.000                    1400 49   4900  3734  0.500  Gd  1.000         1.000   0.000                    1400 45   5700  1035  0.500  Gd  1.500         1.000   0.000                    1400 41   7200  2136  0.500  Gd  2.500         1.000   0.000                    1400 31   3200  3537  0.500  Gd  5.000         1.000   0.000                    1400 30   3700  -3538  0.500  Gd  5.300         1.000   0.000                    1400 20   1300  40    *39  0.500  Dy  0.005         1.000   0.000                    1400 60   1300  104   *40  0.500  Dy  0.040         1.000   0.000                    1400 57    500  120   *41  0.500  Dy  0.050         1.000   0.000                    1400 55   4900  5842  0.500  Dy  0.500         1.000   0.000                    1400 48   5500  3643  0.500  Dy  1.000         1.000   0.000                    1400 44   6200  1044  0.500  Dy  1.500         1.000   0.000                    1400 40   6100  -2345  0.500  Dy  2.500         1.000   0.000                    1400 34   3200  -6146  0.500  Dy  5.000         1.000   0.000                    1400 30   3200  -4747  0.500  Dy  5.300         1.000   0.000                    1400 27   1800  --    *48  0.500  Ce  0.005         1.000   0.000                    1400 70   1300  121   *49  0.500  Ce  0.050         1.000   0.000                    1400 68   3900  6550  0.500  Ce  0.500         1.000   0.000                    1400 59   4300  4251  0.500  Ce  1.000         1.000   0.000                    1400 53   5100  2152  0.500  Ce  1.500         1.000   0.000                    1400 45   4200  453  0.500  Ce  2.500         1.000   0.000                    1400 33   4000  -1554  0.500  Nd  0.150         1.000            MnO  0.010                    1400 51   6600  4955  0.500  Nd  0.150         1.000            MnO  0.100                    1400 50   6500  4756  0.500  Nd  0.150         1.000            MnO  0.180                    1400 55   6800  4057  0.500  Nd  0.150         1.000            MnO  0.210                    1400 --   --    --    *58  0.500  Nd  0.150         1.000            ZnO  0.010                    1400 60   6900  4759  0.500  Nd  0.150         1.000            ZnO  0.100                    1400 58   7000  4560  0.500  Nd  0.150         1.000            ZnO  0.180                    1400 53   7200  3961  0.500  Nd  0.150         1.000            ZnO  0.210                    1400 --    800  --    *__________________________________________________________________________ 
    
     
                                           TABLE 3__________________________________________________________________________                         Relative   Tempera-                    Sintering                         Dielec-    tureComposition of Ceramic Dielectrics                    Tempera-                         tric       Coeffi-Sample Ln.sup.1  Sintering                    ture Constant                              Value of Q                                    cient τ.sup.fNo. x  (w = 0)      y  2z Agent                 a  (°C.)                         (ε.sub.r)                              (at 3 GHz)                                    (ppm/°C.)                                          Note__________________________________________________________________________62  0.500  Nd  0.150         0.400   0.000                    1400 28   1600  35    *63  0.500  Nd  0.150         0.500   0.000                    1400 60   6400  2164  0.500  Nd  0.150         0.750   0.000                    1400 61   6700  5065  0.500  Nd  0.150         1.250   0.000                    1400 64   6500  4066  0.500  Nd  0.150         1.500   0.000                    1400 62   5200  3967  0.500  Nd  0.150         2.000   0.000                    1400 63   5400  3768  0.500  Nd  0.150         3.100   0.000                    1400 76   4600  135   *69  0.500  Nd  0.150         1.000   0.000                    1100 23    800  --    *70  0.500  Nd  0.150         1.000   0.000                    1150 27    900  --    *71  0.500  Nd  0.150         1.000   0.000                    1200 60   6000  4172  0.500  Nd  0.150         1.000   0.000                    1300 61   5700  4773  0.500  Nd  0.150         1.000   0.000                    1500 62   6200  4874  0.500  Nd  0.150         1.000   0.000                    1600 63   5600  4975  0.500  Nd  0.150         1.000   0.000                    1650 unmeasured owing to                                          *                         dissolution76  0.500  Nd  0.150         1.000            MnO  0.100                    1150 29   1100  47    *77  0.500  Nd  0.150         1.000            MnO  0.100                    1200 60   6500  4178  0.500  Nd  0.150         1.000            MnO  0.100                    1300 60   6000  4179  0.500  Nd  0.150         1.000            ZnO  0.100                    1150 27    900  44    *80  0.500  Nd  0.150         1.000            ZnO  0.100                    1200 59   6800  4681  0.500  Nd  0.150         1.000            ZnO  0.100                    1300 60   7100  4782  0.500  La  0.150         1.000   0.000                    1400 70   4900  9383  0.500  La  0  1.000   0.000                    1400 57   3400  800   *84  0.500  La  0.001         1.000   0.000                    1400 61   3900  148   *85  0.500  La  0.010         1.000   0.000                    1400 52   4200  125   *86  0.500  La  0.100         1.000   0.000                    1400 49   4300  6987  0.500  La  1.000         1.000   0.000                    1400 51   4700  6388  0.500  La  3.000         1.000   0.000                    1400 47   3500  2189  0.500  La  4.900         1.000   0.000                    1400 43   3400  1190  0.500  La  5.500         1.000   0.000                    1400 41    360  -100  *91  0.700  La  0.500         1.000   0.000                    1400 64   6300  9392  0.700  La  2.500         1.000   0.000                    1400 59   3800  1993  0.700  La  6.000         1.000   0.000                    1400 43    560  0     *94  1.000  La  3.000         1.000   0.000                    1400 85    490  490   *95  1.000  La  6.000         1.000   0.000                    1400 47    300  580   *__________________________________________________________________________ 
    
     
                                           TABLE 4__________________________________________________________________________                           Relative   Tempera-                      Sintering                           Dielec-    tureComposition of Ceramic Dielectrics                      Tempera-                           tric       Coeffi-Sample Ln.sup.1    Sintering                      ture Constant                                Value of Q                                      cient τ.sup.fNo. x  Ln.sup.2     w  y  2z Agents                   a  (°C.)                           (ε.sub.r)                                (at 3 GHz)                                      (ppm/°C.)                                           Note__________________________________________________________________________96  0.500  Nd 0.500        0.500           1.000   0.000                      1400 63   4800  62  Sm97  0.500  Nd 0.500        0.500           1.000   0.000                      1400 60   4100  61  Gd98  0.500  Nd 0.500        0.500           1.000   0.000                      1400 60   4200  60  Dy99  0.500  Nd 0.500        0.500           1.000   0.000                      1400 67   3600  64  Ce100 0.500  Sm 0.500        0.500           1.000   0.000                      1400 58   4900  61  Gd101 0.500  Sm 0.500        0.500           1.000   0.000                      1400 60   4200  60  Dy102 0.500  Sm 0.500        0.500           1.000   0.000                      1400 57   4200  63  Ce103 0.500  Sm 0.500        0.500           1.000   0.000                      1400 51   4500  59  Dy104 0.500  Gd 0.500        0.500           1.000   0.000                      1400 60   4000  63  Ce105 0.500  Dy 0.500        0.500           1.000   0.000                      1400 61   4200  51  Ce106 0.500  Nd 0.010        0.500           1.000   0.000                      1400 52   10000 25  La107 0.500  Nd 0.100        0.500           1.000   0.000                      1400 56   11500 25  La108 0.500  Nd 0.200        0.500           1.000   0.000                      1400 59   12100 37  La109 0.500  Nd 0.300        0.500           1.000   0.000                      1400 61   11300 44  La110 0.500  Nd 0.400        0.500           1.000   0.000                      1400 64   10800 56  La111 0.500  Nd 0.500        0.500           1.000   0.000                      1400 66   9700  63  La__________________________________________________________________________ 
    
     
                                           TABLE 5__________________________________________________________________________                           Relative   Tempera-                      Sintering                           Dielec-    tureComposition of Ceramic Dielectrics                      Tempera-                           tric       Coeffi-Sample Ln.sup.1    Sintering                      ture Constant                                Value of Q                                      cient τ.sup.fNo. x  Ln.sup.2     w  y  2z Agents                   a  (°C.)                           (ε.sub.r)                                (at 3 GHz)                                      (ppm/°C.)                                           Note__________________________________________________________________________112 0.500  Nd 0.600        0.500           1.000   0.000                      1400 66   8300  65  La113 0.500  Nd 0.700        0.500           1.000   0.000                      1400 68   5200  73  La114 0.500  Nd 0.800        0.500           1.000   0.000                      1400 69   5000  77  La115 0.500  Nd 0.900        0.500           1.000   0.000                      1400 70   4800  91  La116 0.500  Nd 0.500        0  1.000   0.000                      1400 56   3500  780  *  La117 0.500  Nd 0.500        0.001           1.000   0.000                      1400 57   4100  190  *  La118 0.500  Nd 0.500        0.010           1.000   0.000                      1400 55   5100  160  *  La119 0.500  Nd 0.500        0.100           1.000   0.000                      1400 54   4100  71  La120 0.500  Nd 0.500        1.000           1.000   0.000                      1400 49   4300  53  La121 0.500  Nd 0.500        3.000           1.000   0.000                      1400 46   3900  18  La122 0.500  Nd 0.500        4.500           1.000   0.000                      1400 43   3300  -3  La123 0.500  Nd 0.500        5.500           1.000   0.000                      1400 35   870   -105 *  La124 0.700  Nd 0.500        0.500           1.000   0.000                      1400 65   6900  78  La125 0.700  Nd 0.500        4.500           1.000   0.000                      1400 46   3300  11  La126 0.700  Nd 0.500        6.000           1.000   0.000                      1400 44   950   8    *  La__________________________________________________________________________ 
    
     As obvious from the results in Tables 1-5, the ceramic dielectrics according to Examples have a high relative dielectric constant (.di-elect cons. r ), 30-70, and a small dielectric loss because of a large value of Q, 3000 or more at a measuring frequency of 3 GHz, and the temperature coefficient of resonant frequency (τ f ) can be controlled to be a particular value within the range of +100° to -100 ppm/°C. by changing the ratio (x) of MgO to CaO, or the ratio (y) of (xMgTiO 3 .(1-x)CaTiO 3 ) to (Ln 1   1  -w Ln 2   w ) 2  Ti 2z  O 3+4z . And by setting the sintering temperature at a temperature of 1200°-1600° C., a ceramic dielectrics having the above excellent electric characteristics can be manufactured. 
     On the other hand, among the ceramic dielectrics according to Comparative Examples, those having x of less than 0.20 or more than 0.80, y of less than 0.05 or more than 5.0, z of less than 0.25 or more than 1.5, and a of more than 0.2, had at least one of Q, relative dielectric constant (.di-elect cons. r ) and temperature coefficient of resonant frequency (τ f ) outside the above ranges. As a result, it is difficult to use them as a material for a resonator, a filter or the like. 
     And as for the ceramic dielectrics formed at a sintering temperature of less than 1200° C. or more than 1600° C., the obtained electric characteristics thereof were not desirable, either. 
     POSSIBILITY OF INDUSTRIAL APPLICATION 
     Ceramic dielectrics according to the present invention can be used as a material for a high-performance resonator processing a signal in the microwave-bandwidth, a filter, a capacitor or the like.