Study And Preparation Of BaTiO₃-based NTC Ceramic Thermistors

At temperature below the Curie point, the BaTiO3-based ceramics presents g ood character of NTC (Negative Temperature Coefficient). The NTC character of BaTiO3-based ceramics is rare studied and reported. High room temperature re sistivity (ρ25) and low B constant thermistors have a broad market application perspective, widely used for temperature measurement and compensation, inrush current limiting, etc. But according to the semi-conduction theory, it is hard t o synthesis using the traditional methods.The aim of this work is to synthesis and study highρ25 and low B consta nt BaTiO3-based NTC ceramic thermistors. Solid-phase synthesis is used, addin g Pb to shift the Curie point, doping ND2O5 to semi-conduct materials and low erρ25, and doping BN to reduce sintering temperature. The influence of proces s and formulas is studied on the BaTiO3-based NTC materials. Main conclusio ns follow as:(1) Sintering temperature has a major effect on the materials. The relations hip ofρ25 and sintering temperature is U-shape. Samples show better NTC cha racter at sintering temperature 1180℃. Appropriate time of heat preservation te mperature helps materials semi-conducting. During this experimentρ25 is minim um when the time of heat preservation is 1h(2) Pb doping is effective for shifting the Curie point. When Pb=60mol%, the Curie point is 330℃which is a lot increment compare to the pure BaTi O3 materials. (3) BN can reduce the sintering temperature, also help semi-conduction. W hen BN=2mol%, samples'=35.7Ω·cm. Nb2O5 promotes semi-conduction and 1o werρ25. Also it can inhibit grain growth.(4)ρ25 of synthesized samples is above 1.3k and constant B is below 1k. It is typical highρ25 and low B NTC thermistor. The Curie point is 330℃, s howing good application perspective.