A Study On Modified Pb-Based Perovskite Microwave Dielectric Ceramics

Along with the miniaturization and integration of communication equipments,microwave dielectric ceramics have been paid wide attention to as the essential material for microwave components, such as dielectric resonator, frequency filter, oscillator,and so on. Three basic requirements for microwave ceramics have been defined: a high dielectric constant , a high Q-value (or a low dielectric losses), a near-zero temperature coefficient of resonant frequency .The paper analyzes comprehensively dielectric properties of microwave dielectric ceramics of (PbCa)(MgNb)O3 series. Aiming at the three necessary requirements for microwave dielectric ceramics used in mobile communication, the paper investigates the characteristic modification by A-Site and B-Site substitutions of Pb-based perovskite (PbCa)(MgNb)O3 material and discusses the influence of these two substitutions on crystal structure, microstructure and microwave dielectric properties of the material. The main content includes:B-Site , and substitutions greatly decrease the dielectric losses of (PbCa)(MgNb)O3 system ceramics under electric field; because of the different characteristics of different ions and the influence of pyrochlore phase created in system, B-Site and ion substitutions increase the dielectric constant of the system, whereas ion substitutions decrease the dielectric constant of the system. Because of the effect of temperature coefficient of dielectric constant and tolerate factor t value, the temperature coefficient of resonant frequency of the system have also changed. , ion substitutions at A-Site greatly decrease the dielectric constant of the system. , ions entering A-Site can eliminate the oxygen vacancy in the system and raise the quality value of the system. With the increase of La, Nd content, the tolerate factor t value of the system and also its temperature coefficient of resonant frequency decrease gradually. The paper studies the synthesis techniques of microwave dielectric ceramics of (PbCa)(MgNb)O3 system, which include the influence of balling time, sinter temperature and heat preservation time on microstructure and microwave dielectric properties.