Preparation and Electrical Properties of Sn Doping Mnnifeo4 Ntc Ceramic

Abstract

Sn doping MnNiFeO 4 NTC ceramic was prepared by the low temperature solid phase reaction route(LTSPR). The as-synthesized powder precursors were characterized by TG-DSC, FTIR and XRD. The crystalline phase and microstructure were characterized by XRD, SEM, EDS and XPS for the sintered pellets. The temperature dependent properties of resistivity were measured for the thermistors and the aged samples by self-made equipment. Experimental results indicate that a singe phase ceramic powder can be prepared by the LTSPR at as low as 750°C;the effects of Sn doping are much remarking on the sintering behavior, microstructure and electrical properties of the thermistors. The specific resistivity and B-value of the samples tend to increase with Sn doping amount increasing, in which MnNi 0.91 Sn 0.09 FeO 4 has a maximum specific resistivity of 32.62K Ω.cm and a maximum B-value of 3928K. Compared with free-Sn MnNiFeO 4 , Mn 1-x Sn x NiFeO 4 (X=0.03 and 0.06) and MnNi 0.91 Sn 0.09 FeO 4 have a lower aging rates in the air due to the stiochiometric cooling effect from Sn suppressing and structure stabilizing effect, and the oxidation hindrance during aging for the higher densification and a perfect microstructure.

Keywords: NTC ceramic, low temperature solid state reaction, microstructure, electrical properties.