Preparation and Characteristics of Low-Resistance,High Power PTCR Material and Its Heating Element in Automobile Application
Huang Zhongzang Lu Hongming (Shanghai Institute of Ceramics,Academia Sinica)
PTCR material bated on(Ba-Pb)TiO_3 solid solution was prepared by using themixed oxide method.La_2O_3 and Nb_2O_5 were added as co-donor,Al_2O_3-SiO_2-excessBaCo_3 and Mn ion with a fixed ratio were selected as the additives,multi-stagesoaking and fast heating procedure were used in sintering process.The property ofa typical sample is as follows:T_c:180±5℃;ρ_v at room temperature:50Ω.cm;Δρ_v(ρ_(vmax)/ρ_(vmin)):10~4.Manifold heaters used for Shanghai Sontana and Beijing Jeep213 were assembled with the heating elements made of the above PTCR material,and exhibit a quite good performance.In the experiment,the relation between composition,process,microstructureand property of the PTCR material was studied.The samples doped with Sb_2O_3exhibit a quite low resistivity at room temperature and those co-doped with La_2O_3and Nb_2O_5 can form a good PTCR anomaly:the additives to form liquid phase du-ring sintering can improve the performance of the sintering behavior and grainboundary property;the introduction of Mn ion changes the resistivity at room tem-perature and enhances largely PTCR anomaly;multi-stage soak and fast heatingprocedure produce a suitable microstructural development and are beneficial to PTCReffect;sintering in N_2 atmosphere and post-treating in air reduce the resistivity atroom temperature but exhibit no substantial improvement of PTCR anomaly of thesamples under the studied condition.
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