攙雜Nb元素之Z5U-BME陶瓷電容器的介電和電學性質之研究

Abstract

本論文內容，主要在於研發製作Z5U-BME鈦酸鋇陶瓷電容器之介電 材料，在實驗中我們以鎳電極共燒的方法將試片在還原氣氛底下燒結，並 經過一適當的退火程序以彌補在還原氣氛下所造成的氧缺陷．根據我們的 研究結果得知Dy和Nb的攙雜有助於介電常數的提高，介電損失的降低和延 長電容器的生命期．此外我們發現在攙雜Dy和Nb原素的試片中，隨著Dy和 Nb攙雜量的提高，半導化行為將會出現，我們推測其原因可能是Dy和Nb攙 雜量的提高導致施體和受體的電荷不平衡．對於Nb攙雜的試片，其居里溫 度點大約在2度C左右，除此之外我們也做了積層式陶瓷電容器的電流和電 壓的量測，藉著分析電流和電壓的關係，試片的電流模型就可分辨出來， 一般來說這些電流模型可分為：歐姆，空間電荷箝制電流(點電極)，和空 間電荷箝制電流(平面電極)．為了得到良好的介電性質，一些實驗製程上 的參數如：B/A 的比例，施體和受體元素的選擇燒結的氣氛，燒結助劑的 選用，錳元素的攙雜量，退火的溫度和氣氛，都必須控制在適當的條件． Barium titanate doped with various amounts of CaCO3, ZrO2, Dy2O3,Nb2O5, and MnO2 was used for the preparation of Z5U-BME dielectrics.The dielectric samples with nickel electrodes were sintered in low oxygen partial pressure to prevent the oxidation of the electrode,and their electrical and hpysical properties were measured. Additionsof Dy and Nb into the samples could obtain higher dielectric constant, lower dissipation factor, and prolonging lifetime. Besides, it wasfound that the dissipation factor of the sample was sensitivelydependent on the amounts of Nb and Dy addition. The dielectric sample lost their properties and became semiconductive if excess of Nb or Dywas used. The Curie point is about = 2oC for the samples doped with Nb. Additionally, the current-voltage characteristics of multilayer capacitorswere also measured and analysized. The characteristic of the devicemeasured at room temperature is ohmic on the basis of 1 power voltage-current relationship. The near 3/2 power current-voltage characteristic(I~V3/2) of specimens measured at high temperature can be attributed toelectron emission from electrode points. The quardratic behaviour (I~V2)observed for the samples measured at higher temperature represent spacecharge limited emission from near planar electrodes.