New negative temperature coefficient ceramics in Zr-doped CaCu3Ti4O12 system

Abstract

In this study, negative temperature coefficient (NTC) ceramics based on CaCu3Ti4-xZrxO12(0 ≦ x ≦ 0.15) compositions have been successfully synthesized by traditional solid-state method. X-ray diffraction results show that the major phase of all samples is CaCu3Ti4O12 (CCTO) phase with body-centered cubic structure. The substitution of Zr4+ for Ti4+ inhibits the grain growth of CaCu3Ti4-xZrxO12 ceramics and greatly reduces the grain size. The results of X-ray photoelectron spectroscopy fully confirm the coexistence of Cu+/Cu2+ and Ti3+/Ti4+ ions, which are one of the important reasons for conductivity of CaCu3Ti4-xZrxO12 samples. There is a good linear relationship between the natural logarithm of resistivity and reciprocal temperature of all ceramic samples, which is consistent with NTC behavior. The obtained values of ρ150, B150/550 and Ea of the sintered samples are in the range of 1.62 × 105–3.39 × 105 Ω cm, 6378–6593 K and 0.550–0.568 eV, respectively.