Synthesis of NTC thermistors with screen printing method from natural yarosite minerals

Abstract

NTC thermistors can make from a mixture of metal oxides. Fe2O3 is a metal oxide contained up to 93.80% in the natural yarosite mineral and has the potential to be used as a material for making thermistors. The objective of this research is to use Fe2O3 from yarosite and Fe2O3 from imports in the production of NTC thermistor and to determine the effect of adding ZrO2 to a mixture of Fe2O3 from yarosite, ZnO and CuO in the manufacture of thick-film oxide ceramic NTC thermistors. Oxide ceramic powder is synthesized, using the sol-gel method. Furthermore, oxide ceramic powder was made into thick-film oxide ceramics made by screen printing technique with a sintering temperature of 1100°C for 2 hours, then characterized using XRD and SEM. After a thick-film oxide ceramic was coated, with silver paste, an NTC thermistor was obtained and measured its electrical resistance to temperature using a multimeter and temperature controller. The results of the analysis of XRD characterization reveal that the crystal system of the ceramic mixture from the samples was rhombohedral. Based on the results of SEM analysis, the addition of ZrO2 doping showed a change in grain size to be smaller. NTC thermistors with raw materials Fe2O3 from yarosite, ZnO, and CuO (Sample I) have resistance which decreases with increasing temperature according to the characteristics of NTC thermistors and has better electrical characteristic than Fe2O3 from imports, ZnO, and CuO (Sample III) for NTC thermistor applications that are preferred commercially. The addition of ZrO2 doping (Sample II) increases the resistance.