Low Resistivity, High-pressure Barium Titanate-based Ptcr Ceramics Research And Preparation

For its unique resistivity-temperature characteristics, PTCR-barium titanate is now a common electrical device with many applications, such as degaussers in TV screens and computer monitors, self-regulated heaters, current suppressors, sensors, and automobiles (in each of which about 50 or 60 motors containing low-resistivity PTCR devices are used in door lock, power window, power seat, etc systems.). The research of preparation of high performance BaTiO₃-based PTCR ceramics with low room temperature resistivity, high ratio of lg(R_max/R_min), and high withstanding voltage has been a focal point in the field of inorganic nonmetal materials since the PTCR effect of doped barium titanate materials was discovered. The preparation and doping method influences the electrical properties of barium titanate strongly. Sol-gel method can prepare multicomposition barium titanate powders. To get high performance PTCR ceramics, Sol-gel method and China-made raw materials were used to prepare B-doped and Nb-doped barium titanate ceramics respectively. The effect of dopant and sintering process on the electrical properties of barium titanate ceramics were analysed by TG-DSC analysis and SEM photoes.This MD dissertation is divided into three parts.In part 1, boron-doped barium titanate ceramics was prepared by Sol-gel method, and the effect of Boron content and sintering temperature on electrical properties and microstructure was investigated. The results show that not only its sintering temperature can be lowered, but also the withstanding voltage can be improved largely.In part 2, Double-donor Nb,Y-codoped barium titanate ceramics was prepared by Sol-gel method with H₃[Nb(O₂)₄] as raw materials, and the effect of Niobium content and cooling rate on electrical properties and microstructure was investigated. The results show that high performance PTCR ceramics could be obtained by the optimization of the content ratio of Nb/Y.In part 3, high performance BaTiO₃-based PTCR ceramics for refrigerator motor starter was prepared by sol-gel method. Based on the optimized composition, 5molPTCR ceramics powders for refrigerator motor starter was prepared. The orthogonal experiment was successfully used to design and optimize the sintering process, and the influence of sintering factors on ceramics materials was discussed by the orthogonal experiment.