摻雜鐠之氧化鋅變阻器的電學性質與微觀結構研究

Abstract

本論文的目的是研究摻雜鐠(Pr)氧化鋅變阻器。首先，我們在製造變阻器 的實驗過程中，得到最佳的製程條件並製做出特性良好的變阻器，也就是 具有高非線性係數(.alpha.)，低漏電流和高穩定特性。其次，我們利用 各種量測儀器配合理論的分析，計算變阻器的一些基本參數，並研究燒結 溫度對於氧化鋅變阻器各種電學性質的影響。我們發現特性佳的變阻器具 有能障箝定(pinning)的現象，此現象和變阻器的電流電壓特性有極密切 的關係。此外，經由微觀結構的觀察，我們發現在高於1300.degree .C燒 結 時有液相產生，並且有氧化鐠的相轉變。經發現液相燒結對於變阻器 的電學性質和微觀結構有很大的影響。氧化鋅變阻器是用來保護電子電路 系統，它的穩定性攸關被保護電路系統的運作，因此變阻器的穩定性是非 常重要。在本文的最後，我們利用突波產生器測試變阻器試片，研究突波 對變阻器電學性質的影響，經由實結果我們得知摻雜鐠氧化鋅變阻器有很 好的突波吸收能力和穩定性。 Znic oxide varistors containing rare earth metal and cobalt oxide which exhibit nonohmic current-voltage characteristics were investigated. In this study, the sample sintered at 1300 .degree.C for 1 hour possessed the best electrical properties, as characteristized by the highest nonlinear coefficient, lowest leakage current,and lowest degradation. The important physical parameters associated with varistors were obtained by the electrical properties measurements and applying basic theory. The pinning effect of voltage- dependent potential barrier was observed at these samples which exhibit good varistor properties. It can be used to explain the high nonlinear current-voltage characteristic of these samples. In addition, according to microstructural observations, we found the liquid phase sintering occurred above 1300 .degree.C, and there exists a phase transformation of praseodymium oxide. It was found that the liquid phase plays an important role on the electrical properties as well as on the microstructure of the ZnO varistor. The stability of I-V characteristics of the varistors has been investigated by using surges withstanding stability test.