Electrical Characteristics of Nb Doped BaTiO3 Ceramics

Abstract

The Nb doped BaTiO3 ceramics, with different Nb2O5 content, ranging from 0.5 to 2.0 at.% Nb, is investigated regarding their microstructure and electrical characteristics in this paper. The Nb/BaTiO3 ceramics is prepared by the conventional solid state reaction and sintered at 1320 °C in an air atmosphere for 2 h. As acceptor dopant Mn in concentration of 0.01 mol% is added. For low doped samples (0.5 mol% Nb), the characteristic is homogeneous and fine grained microstructure with grain size from 0.5 to 2 μm. Increasing the additive content results in the grain size increasing so that the samples doped with 2.0 mol% Nb the average grain size reaches 10 μm. The dielectric characteristic of Nb doped BaTiO3 ceramics like dielectric constant, dissipation factor and resistivity have been measured by using LCR-Meter Agilent 4284A in the frequency range 20 Hz–1 MHz and Agilent E4991A RF Impedance/Material Analyzer for high frequency measurements (1 MHz–3 GHz). Dielectric constant and tangent losses after initial large values remains nearly independent of frequency greater than 10 kHz. Dielectric measurements were carried out as a function of temperature up to 180 °C. The low doped samples (0.5Nb/BaTiO3) sintered at 1320 °C, display the high value of dielectric permittivity at room temperature, e r = 3225. A nearly flat permittivity-temperature response is obtained in specimens with 2.0 at.% additive content. The Curie–Weiss and modified Curie–Weiss law is used to clarify the influence of dopant on the dielectric properties and BaTiO3 phase transformation. All investigated samples have an electrical resistivity ρ > 106 Ωcm at room temperature. New aspect here is fractal correction, introduced as slight variation of temperature T entered from outside, due to three fractal factors α S , α P and α M being responsible for complex geometry of both morphologic and dynamic nature. This correction, naturally has impact on the Curie–Weiss low, which is stressed in this paper.