Effects of Zn-doping on the electrical properties of ZnxFe2.5−xNi2Mn1.5O8 (0≤ x ≤ 0.8) NTC ceramics by co-precipitation method

Abstract

The ZnxFe2.5-xNi2Mn1.5O8(0 ≤ x ≤ 0.8) ceramics with different compositions were synthesized by co-precipitation method. The effects of Zn doping on the structure, electrical properties and stability of the ceramic samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), electrical measurement and X-ray photoelectron spectroscopy (XPS) analysis. It was found that, as the Zn doping content in the ZnxFe2.5-xNi2Mn1.5O8 samples increased, both the grain size and the density decreased. The XPS analysis confirmed the conduction of as-sintered ceramic structure was mainly due to hopping of electrons between Mn3+/Mn4+ and Fe2+/Fe3+ ions. The values of B 25/50 constant, ρ 25 and E a of ZnxFe2.5-xNi2Mn1.5O8 ceramic samples were in the range of 5375–4177 K, 9042–18 KΩ•cm and 0.464–0.360 eV, respectively. The values of relative resistance drift (ΔR/R 0 ) were in the range of 0.58–2.78% and had a minimum value with the Zn content of x = 0.2 after aging test at 125 °C for 500 h. This suggests that the electrical properties of ZnxFe2.5-xNi2Mn1.5O8 ceramic system can be adjusted to desired values by controlling the Zn ion doping content. Besides, the stability of Mn-Ni-Fe-O ceramic can be effectively improved by Zn doping.