| Low Temperature Co-fired Ceramics (LTCC) is a components integration technology rose in recent years. It has become the preferred method to achieve the miniaturization, integration and modularization of various microwave components worked in the circuits. It is widely used in military and civilian communication systems. Microwave dielectric ceramics are the key materials of LTCC technology. High permittivity dielectric ceramics are mainly used in civilian mobile connunication systems as resonators and filters which work at low frequency. In order to reduce the production costs, the microwave dielectric ceramics are required to be sintered with Ag or Cu at low temperature and have high permittivity.For China, the development and application research of low and middle permittivity LTCC materials are much more advanced than those of the high permittivity (εr>80) ones. CaO-Li2O-Ln2O3-TiO2 system has high permittivity (εr)>100, low dielectric loss and adjustable temperature coefficient of frequency (τf). It is potential for application. However, there are still several problems as follows: (1) The Q×f value decrease considerably with the decrease ofτf. (2) Though the sintering temperature can be decreased to about 900℃, theεr and Q×f value decreased too low to meet the requirements of microwave electron components. (3) The research on tape-casting and co-firing with Ag is limited. Therefore, it is of much importance to decrease the sintering temperature of CaO-Li2O-Ln2O3-TiO2 while keep relative highεr and Q×f value for the research on high permittivity LTCC microwave dielectric materials.For the purpose to prepare high permittivity ((εr=80～90) LTCC microwave dielectric materials, ions substitution, low temperature sintering and application properties of (Cai1-xNd2x/3)TiO3 ceramics were studied in this dissertation. The main research results are as follows:1. The A and B site ions were substituted to improve the microwave dielectric properties of (Ca1-xNd2x/3)TiO3. (1) Substituted the A site ions Nd3+ and Ca2+ by Sm3+, Bi3+ and Zn2+, Mg2+, respectively to modify the (Ca1-xNd2x/3)TiO3 ceramics. Limited solid solutions were formed when Nd substituted by Bi . It was found that theεr increased with the Bi3+ substitution while the Q×f value decreased. With the decreasing radius of A site ions (Sm3+, Zn2+, Mg2+), theεr andτf were decreased and the Q×f values were increased. Sm3+ substitution could keep theεr up to 100 and improve theτf and Q×f. (Ca0.61Sm0.26)TiO3 sintered at 1300℃for 2h exhibited the microwave dielectric properties ofεr=102.59, Q×f=12782GHz,τf =+183ppm/℃. (2) Substituted the B site ions Ti4+ by Mn and Sn4+ respectively to modify the (Ca1-xNd2x/3)TiO3 ceramics. Both of them could form complete solid solutions. There were two kind of substitution styles because of the alterable valence of Mn. Microwave dielectric properties could not be improved by Mn substitution. However, improvement of the dielectric properties could be achieved by Sn4+ substitution.εr=103.19, Q×f=13498GHz,τf=+145ppm/℃were acquired when (Ca0.61Nd0.26)(Ti0.98Sn0.02)O3 ceramics sintered at 1350℃for 2h. (3) The dielectric properties of A-site Zn2+ and B-site Sn4+ ions harmonizing substitution in (Ca1-xNd2x/3)TiO3 ceramics were deteriorated. (4) On all accounts, the (Ca0.61Nd0.26)(Ti0.98Sn0.02)O3 ceramics possesses excellent dielectric properties. However, it is necessary to reduce its sintering temperature to meet the requirement of LTCC technology.2. The sintering temperature of (Ca, Nd)(Ti, Sn)O3 ceramics was decreased by adding various sintering additives. (1) The sintering temperature of (Ca, Nd)(Ti, Sn)O3 ceramics was decreased to 1000℃, 1100℃and 950℃respectively with H3BO3-CuO, BaCu(B2O5) and H3BO3-CuO-Li2CO3 addition. (2) H3BO3-CuO and H3BO3-CuO-Li2CO3 additives existed as liquid phase during the sintering process, while BaCu(BO5) reacted with (Ca, Nd)(Ti, Sn)O3 to form BaNd2Ti5O14. (3) The (Ca, Nd)(Ti, Sn)O3 ceramics with 5wt% (H3BO3-CuO) - 0.5wt% Li2CO3 could be sintered at 950℃and exhibited excellent dielectric properties ofεr=94.57, Q×f=8296GHz,τf=+183ppm/℃. However, theτ/f still need to be decreased.3. (Ca, Nd)(Ti, Sn)O3- (Li1/2Nd1/2)TiO3 composites exhibited near-zeroτf value and highεr with H3BO3-CuO-Li2CO3 addition sintered at 900℃. Rhombic perovskite main phase and rutile secondary phase were observed. The H3BO3-CuO-Li2CO3 doped 0.4(Ca, Nd)(Ti, Sn)O3-0.6(Li1/2Nd1/2)TiO3 ceramics sintered at 900℃for 2h exhibited excellent properties ofεr=90.57, Q×f= 3426GHz,τf=+9ppm/℃.4. The characteristics of (Ca, Nd)(Ti, Sn)O3-(Li1/2Nd1/2)TiO3 aqueous slurry and the interface of co-fired ceramic tape and Ag were investigated. WB4010 emulsion binder improved the dispersing of H3BO3 in the slurry. The tapes shaped by tape-casting had smooth surface and uniform structure. The interface of the ceramic and the Ag electrode was compactness and no element diffusion was observed. It was a promising high permittivity LTCC microwave dielectric materials used for preparation of multilayer microwave components.
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