Effects of Zn-doped on the microstructure and electrical properties of Mn1.5 − xCo1.2Cu0.3ZnxO4(0 ≤ x ≤ 0.5) NTC ceramics

Abstract

In this paper, the Mn1.5 − xCo1.2Cu0.3ZnxO4 (0 ≤ x ≤ 0.5) negative temperature coefficient (NTC) ceramics were attained by the traditional solid state reaction method. The effects of Zn addition on microstructure and electrical properties were characterized by thermo-gravimetry–differential scanning calorimetry, X-ray diffraction, scanning electron microscope, electrical measurement and X-ray photoelectron spectroscopy analysis. It was found that the resistivity decreased slightly with increasing Zn ions content for x ≤ 0.2, but increased remarkably for higher Zn ions content. The values ρ25 and B25/50 of Mn1.5 − xCo1.2Cu0.3ZnxO4 (0 ≤ x ≤ 0.5) NTC thermistors were in the range of 126–706 Ω cm and 3323–3714 K, respectively. The values of relative resistance drift (ΔR/R0) were in the range of 2.7–1.13% and had a minimum value with the Zn content x = 0.5 after aging test at 125 °C for 500 h. This suggests that the electrical properties can be adjusted to desired values by controlling the Zn ion doping content. Most importantly, the stability of Mn1.5 − xCo1.2Cu0.3ZnxO4 ceramic can be effectively improved by Zn doping.