降溫速率對鑭加成鈦酸鋇基正溫度電阻係數的影響效應

Abstract

已有諸多研究深人探討過影幾 PTCR 效應的因素：如顯微結構，不同添加物與添加物的量，降溫速率，晶粒大小，燒結溫度與時間等0而對於鋇多量造成二次相的析出，進而影響 PTCR的效應，有必要作進一步的研究。本實驗將探討降溫速率對二次相析出與二次相對室溫晶界電阻的影響。降溫速率亦影響高與最低電阻的比值和最低的電阻值。另外，降溫停留時間也是影響二次相析出的因素。本文將利用複數平面阻抗圖分析晶界電阻，並作 I-V 特性的應用。將分別探討錳加成與錳加成鋇多量影響 PTCR 的現象。

The magnitude of the PTCR which related to many factors including ceramic microstructure, donor and acceptor dopant concentration, cooling rate, grain size, sintering temperature, TiO2 excess, BaO excess, and sintering time, etc. has been reported. Recently, the barium titanate ceramics with Ba-rich compositions exhibiting large PTCR effect have, however, been produced. More attempts need to be made to provide further information about the role of barium-rich phase in the PTCR effect. In the present study, significant amount of Barium-rich phase intended to be produced by controlling the cooling conditions of barium excess Ba0.8 Sr0.2 TiO3 samples and the effect of this second phase on the PTCR effect and grain boundary resistanece was determined. Variation of the amounts of excess BaO influences the room temperature resistivity and the PTCR effect. The magnitude of the PTCR effect and the resistance of grain boundary decrease with increasing cooling rate. The amounts of Ba-rich phase precipitate c aracteristically with the cooling rate. More Ba-rich phase was detected on the grain boundary for the sample cooled by slower rate. The effect of soaking time on the room temperature resistance was analyzed by the complex-plane impedance analysis. In addition, we observe that the excess addition of Mn+2 ion in the sample was the fatal of PTCR effect. The effect on the electrical behanior ot PTCR ceramics with the dopants MnO and BaO was also investigated.