(CaCu3Ti4O12)1-x(Fe3O4)x氧化物介電性質之研究

Abstract

在這論文當中，以氧化鐵(Fe3O4)用不同比例摻雜CaCu3Ti4O12，並以固態反應法以1050℃ 燒結製備樣品。在(CaCu3Ti4O12)0.99(Fe3O4)0.01的樣品，介電常數從104急遽降低至65。CaCu3Ti4O12在TN = 25 K時有反鐵磁相變，在(CaCu3Ti4O12)1-x(Fe3O4)x (x = 0.01, 0.05, 0.1, 0.2, and 0.3) 的樣品，在 TN 以下介電常數會隨溫度降低而減少，提供了電極化與磁性之間的耦合現象。其中(CaCu3Ti4O12)0.95(Fe3O4)0.05 及(CaCu3Ti4O12)0.9(Fe3O4)0.1兩個樣品有擴散相變(Diffuse Phase transition)，由modified Curie–Weiss law，Santos-Eiras equation 及 Vogel–Fulcher relationship，我們知道擴散相變是因為這兩個樣品有ferroelectric relaxor 的特性。

The dielectric properties of (CaCu3Ti4O12)1-x(Fe3O4)x (x = 0.01, 0.05, 0.1, 0.2, 0.3 and 0.4) have been studied, only 1% mixing of Fe3O4 dramatically quenches the huge of 104 down to 65 over the measured temperature range from 15 K to 300 K. At low T, CaCu3Ti4O12 (CCTO) transforms into an antiferromagnetic phase at TN = 25 K. The dielectric constant of (CaCu3Ti4O12)1-x(Fe3O4)x (x = 0.01, 0.05, 0.1, 0.2 and 0.3) shows sharp decrease below TN, providing possible coupling between the polarization and magnetization. In addition, the (CCTO)0.95(Fe3O4)0.05 and (CCTO)0.9(Fe3O4)0.1 ceramics have also shown diffuse phase transition (DPT), which is a typical feature of relaxor ferroelectrics. The modified Curie–Weiss law and Santos-Eiras equation were applied to (CCTO)0.95(Fe3O4)0.05 and (CCTO)0.9(Fe3O4)0.1 ceramics in order to investigate the nature of polarization mechanism. Furthermore, physical parameters such as static freezing temperature TVF fitted by the Vogel–Fulcher relationship, indicated the relaxor nature of these two ceramics.