利用電子鎗蒸鍍並經熱擴散後之摻雜釔的鈦酸鋇陶瓷中電子傳輸行為

Abstract

本論文研究重點在於探討利用電子鎗蒸鍍系統將氧化釔蒸鍍在鈦酸 鋇的基板上,並 經熱擴散將釔趨入(drive in)基板內,對於具有正溫度係 數電阻(PTCR)的基板造成那些電性上的影響.我們發現基板摻雜釔且經擴 散後,在電性上有很大的改變:其導電率隨擴散時間增長而變差.除此之外, 基板上無蒸鍍釔而同時在相同環境及時間下做退火(annealing)的試片用 來與鍍釔的試片做比較,以利觀察釔擴散的效應,和探討退火的影響;由這 項實驗發現對於適當時間下退火的試片,其導電率可獲改善,然當時間增長 時,導電率則再度的變差.我們利用不同型式的缺陷共存在晶界的觀念來解 釋此一現象,而發現我們的實驗結果與文獻上所觀察到的現象有相吻合之 處.另外,對於不同降溫速率而產生不同的缺陷結構, 我們亦有詳細的探 討. A technique for fabricating barium titanate ceramics was proposed here, which was different from the conventional solid- state reaction process. The additive, yttrium, was evaporated onto the polycrystalline BaTiO3 substrate bythe E-gun evaporator system, and then was driven into the substrate by thermaldiffusion. It was found that the Y diffusion by means of this method inspired a great influence on electrical properties. That is, the conductivity decreas-es with annealing time. Besides the experiment of Y-diffusion, the substrate without containing Y was also manipulated at the same environment to make the comparison. And it is showed that the conductivity increased after the approp-riate annealing process and rapid cooling from the latter experiment. Utiliz-ing the concept of the coexistence of different types of defects at the grain boundary, the grain boundary phenomena resulting from the increase in the surface-state density could be explained satisfactorily. Also, the different cooling rates resulting in the different defect structures were investigated in detail.