Defects restoration during cooling and annealing in PTC type barium titanate ceramics |
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| Authors: | Tsai-Fa Lin Chen-Ti Hu I-Nan Lin |
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| Affiliation: | (1) Department of Materials Science and Engineering, National Tsing Hua University, 30043 Hsinchu, Taiwan;(2) Chun-Shan Institute of Science and Technology, Lungtan, Taiwan |
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| Abstract: | The PTC-type BaTiO3 ceramics of similar microstructure are obtained by careful control of a sintering scheme. The defect chemistry of them is modified by varying the cooling rate and annealing conditons. In addition to applying Heywang and Jonker models for explaining the resistivity anomaly of these samples, the outward diffusion of oxygen vacancies (VO), which left excess barium vacancies (VBa) behind, is proposed to be the formation mechanism of surface states. The formation of defect complex consisting of a VO..-Ba pair is assumed to be the cause of small diffusivity of VO in these materials. The phenomena, in which the slower cooling rate raises the resistivity of samples, is ascribed to the higher concentration of excess barium vacancies (VBa) contained in these samples. However, the maximum potential barrier height ( max) of the samples is the same, irrespective of the amount of surface state concentration (Ns) and is estimated to be max = 0.66eV, from the In ( max)-1/Tmax plot. |
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