高介電材料CaCu3Ti4O12 (CCTO) 製備之研究

Abstract

論文研究利用傳統的粉末混合法及溶膠凝膠法製作高介電材料CaCu3Ti4O12 (CCTO)的塊材與薄膜。塊材部份，我們探討燒結溫度及時間對於其介電特性的影響。藉由改變燒結溫度及時間，我們可以發現其介電常數隨著燒結溫度及時間的增加而上升。介電常數上升的主要原因為平均晶粒粒徑的增加，並且符合晶粒界面障壁層電容器的推論。而介電損失則隨著燒結溫度及時間的增加而下降。在本論文的研究中發現，1100oC燒結20小時之CCTO塊材可達到95.2%的理論密度，在頻率1 kHz下的介電常數及介電損失分別為28000及0.16。 薄膜部分，我們改變熱處理溫度從500oC到800oC來研究其介電特性的改變，發現700oC是CCTO薄膜結晶的最低溫度，介電常數也隨著熱處理溫度上升而升高，此部分也可歸因為平均晶粒粒徑的增加。在室溫及100 kHz的頻率下， 800oC熱處理1小時的CCTO薄膜擁有1224的介電常數和0.179的介電損失。

The high dielectric constant material CaCu3Ti4O12 (CCTO) is studied by conventional oxide powder mixing and sol-gel processing. For bulk samples, the effects of sintering temperature and sintering time are discussed. With changing the sintering temperature and sintering time, we can obtain that the dielectric constant increase with increasing sintering temperature and time. 95.2% relative density, 28000 dielectric constant, and 0.16 loss tangent at 1 kHz can be achieved by sintering at 1100□C for 20 hrs. The increase in dielectric constant can be attributed to the increase in average grain size, which is consistent with the grain boundary (internal) barrier layer capacitance (IBLC) theory. For CCTO thin films, we change the annealing temperature from 500□□C to 800□□C and find that the lowest annealing temperature for CCTO thin film to crystallize is 700□□C. The dielectric constant also increases with increasing annealing temperature. It can also be attributed to the increase in average grain size. At room temperature, the dielectric constant and loss tangent of CCTO thin film with annealing temperature at 800□□C for 1 hr are about 1224 and 0.179 at 100 kHz, respectively.