BZT-Based Ceramics With Perovskite Type Structure: Preparation And Dielectric Properties

The investigations and applications of environment-friendly high voltage capacitors with fine properties are imperative due to the miniaturization of electronic equipments as well as the demand of environment protection. This dissertation focuses on the development of dielectric materials with high permittivity, low dielectric loss, high breakdown voltage and low temperature coefficient of capacitor based on barium strontium titanate(BZT) ceramics.Twice burden technology was innovatively introduced into the traditional solid state method and for the rare earth oxide M₂O₃ (M= La,Sm) and M₂O₅ (M= V,Ta) doped, and M₂O₃ (M= La,Sm) and M₂O₅ (M= V,Ta) co-doped barium zirconia titanate (BZT) dielectric ceramics were obtained successfully utilizing this preparation procedure. The effects of preparing conditions and sample compositions on the characters of dielectric ceramics were investigated respectively. It is revealed that temperature stable dielectric ceramics for high voltage capacitor applications can be synthesized using suitable sintering temperature after increasing the addition level of M₂O₃ (M= La,Sm) and M₂O₅ (M= V,Ta).The X-ray diffraction (XRD) meter and environmental scanning electron microscope (ESEM) were employed to confirm the phases and surface morphologies of specimens. It is found that with increasing M₂O₃ (M= La,Sm) and M₂O₅ (M= V,Ta) doping content the BZT based dielectric ceramics are turned into fine-grained multiphase compounds from single-phase perovskites. Nevertheless, M₂O₃ (M= La,Sm) and M₂O₅ (M= V,Ta) addition content has few influences on the phases of current dielectric ceramcis.The subtitution characteristics of M₂O₃ and M₂O₅ in BZT perovskite structure were illustrated according to the average lattice constant. It is indicated that rare earth ions M³⁺ (M= La,Sm) tend to occupy the A sites while M³⁺ ions initially enter A sites as donor dopant and then inhabit B sites as acceptor dopant with increasing doping content. Furthermore, the defect models of present systems were established based on the above replacement traits for M₂O₃. Besides, it is indicated that rare earth ions M⁵⁺ M₂O₅ (M= V,Ta) tend to occupy the B sites as acceptor dopant with increasing doping content. Furthermore, the defect models of present systems were established based on the above replacement traits for M₂O₅.The increasing M₂O₃ (M= La,Sm) and M₂O₅ (M= V,Ta) doping content the BZT based dielectric ceramics with high dielectric constantare promising for applications in high voltage capacitor industry as environment-friendly and temperature stable dielectric materials.