New negative temperature coefficient ceramics in Ca1−x Y x Cu2.5Mn0.5Ti4O12 system

Abstract

The Ca1−x Y x Cu2.5Mn0.5Ti4O12 (x = 0, 0.02, 0.05, 0.1) negative temperature coefficient (NTC) ceramics synthesized by conventional solid state reaction have been investigated. X-ray diffraction analysis has revealed that for 0 ≤ x ≤ 0.05, the phase of as-sintered ceramics is a single CaCu3Ti4O12 phase, nevertheless, for x = 0.1, a second phase Y2O3 appears. The grain size of as-sintered ceramics decreases with increasing Y content. All the ceramic samples prepared show a linear relationship between the natural logarithm of the resistivity and the reciprocal temperature, indicative of NTC characteristics. The electrical resistivity decreases at first and then increases with the increase of the Y content. The electrical conductivity anomaly appearing in these ceramics should be attributed to the substitution of the Y3+ for Ca2+ on one hand and the presence of Y2O3 phase on the other hand.