Grain boundary effect on dielectric properties of (Nd0.5Nb0.5)xTi1-xO2 ceramicsceamics

Abstract

The search for colossal dielectric constant materials is imperative because of their potential for promising applications for the areas of device miniaturization and energy storage. In this work, (Nd0.5Nb0.5)xTi1-xO2 ceramics is prepared via the solid-state reaction route. The microstructure, crystal structures, and dielectric properties of (Nd0.5Nb0.5)xTi1-xO2 ceramics are investigated. It is proved that schottky barrier exists at grain boundary by measuring impedance spectrum of different DC biases and C-V curve. The grain boundary characteristics of the ceramics are studied. It is found that the proper second phase is beneficial to increase the grain boundary resistance and restrain the long range movement of electrons, so that the material keeps low dielectric loss and improves the temperature stability. But too much of second phase will deteriorate performance due to excessive space charges. In addition, all the (Nd0.5Nb0.5)xTi1-xO2 ceramics displays a colossal dielectric constant (>104), especially a high dielectric constant (2.55 × 104) and low dielectric loss (0.023) at 1 kHz and room temperature which can be obtain in (Nd0.5Nb0.5)xTi1-xO2 ceramic with x = 3%. The dielectric properties of (Nd0.5Nb0.5)xTi1-xO2 ceramics can be explained by internal barrier layer capacitor (IBLC) model, which can be optimized by balancing grain size, barrier height and barrier width.