Temperature-stable Barium Titanate Ceramics Containing Niobium Pentoxide

Ian Burn

doi:10.1155/apec.2.241

Abstract

Niobium is known to lower the Curie point and broaden the permittivity peak of barium titanate. However, the distribution of niobium in sintered barium titanate is often not homogeneous, being influenced by such preparation variables as large cation/small cation stoichiometry and firing conditions. In addition to these factors, it was found that, at least up to about 5 mol% Nb, the distribution of niobium in the barium titanate grains could be regulated by small amounts (<1 mol%) of oxides of Co, Mg, Ni or Mn. These oxides appear to form niobates that produce high permittivity solid solutions in the “skins” of the barium titanate grains and permit dielectrics to be obtained with permittivity (K≃¯2000), stable to within ±10% over the temperature range −55℃ to 125℃.

Highlights

The influence of niobium on the temperature dependence of the permittivity of barium titanate has been described by several authors. -a Some inconsistencies in the earlier data 1,2 have been explained by Kahna who found that the addition of Nb to prereacted barium titanate resulted in a homogeneous distribution only under conditions of grain growth during sintering
When the niobium was less than about 3 mol %, some connected porosity was apparent in the ceramic for the firing conditions used, and the presence of some unreacted barium titanate was evident from the secondary capacitance peak
A dense ceramic was obtained for 3.8% Nb, there was no evidence of any significant grain growth during sintering (Figure 2), and some unreacted barium titanate could still be detected

Summary

INTRODUCTION

The influence of niobium on the temperature dependence of the permittivity of barium titanate has been described by several authors. -a Some inconsistencies in the earlier data 1,2 have been explained by Kahna who found that the addition of Nb to prereacted barium titanate resulted in a homogeneous distribution only under conditions of grain growth during sintering. -a Some inconsistencies in the earlier data 1,2 have been explained by Kahna who found that the addition of Nb to prereacted barium titanate resulted in a homogeneous distribution only under conditions of grain growth during sintering. As pointed out by Plessner and West and Rutt,[6] if an additive that lowers the Curie temperature of barium titanate is distributed in a non-homogeneous but controlled manner, the material can be of practical use as a high permittivity (K 2000) temperature.stable dielectric. Dielectrics of this type have been described that contain several mol %. FeB’ or Mg. 8’ 11 It was found in the present work that certain other additives modify the niobium distribution and an attempt has been made to explain this effect

EXPERIMENTAL PROCEDURE

RESULTS

DISCUSSION