Structure and electrical performance of Mn1.5−0.5xCo0.9−0.3xNi0.6−0.2xCuxO4 NTC ceramics prepared by heterogeneous precipitation

Abstract

The spinel-structured ceramics of Mn1.5−0.5xCo0.9−0.3xNi0.6−0.2xCuxO4 negative temperature coefficient (NTC) thermistors were fabricated by heterogeneous precipitation. The precursor powder of Mn1.5Co0.9Ni0.6O4 was first prepared by mixing manganese, cobalt and nickel oxide with a molar ratio of 5:3:2 and calcining at 1100°C for 2h. Cupric carbonate was precipitated onto the surface of the precursor particles by heterogeneous precipitation, and then the powder was pressed and sintered. The Cu-precipitated powders were confirmed by both TGA/DSC analysis and SEM images. The microstructures of the ceramics were predominantly spinel structure and a small amount of NiO rock-salt. In comparison with the samples of the same composition prepared by traditional solid-state methods, ceramics from heterogeneous precipitation powder demonstrate lower electrical resistivity, higher B constants and much better electrical stability.