Substrate Purity Dependence of Heating Characteristics for 15mol% Ca-doped-LaCrO₃ Thin Film Heaters

Abstract

Lanthanum chromite (LaCrO₃) has excellent chemical stability at high temperature. LaCrO₃ doped with alkaline earth metals has high electric conductivity as a heater material having operating temperatures starting from room temperature. The purpose of this study is to fabricate heaters using thin films of LaCrO₃ doped with dopant Ca which is deposited on alumina substrates with different purities by RF magnetron sputtering and evaluate their characteristics under any conditions. Thin films of Ca doped LaCrO₃ shows different heating characteristics with dc current drive for the different purity of alumina substrate. In case of lower purity (95.3%), long term stabilities of LaCrO₃ thin film heaters showed the increase of the residence with increasing time. On the other hands, in case of high purity (approximately 99.5%), the resistance was almost constant. It is speculated that impurities, such as SiO₂, contained in a alumina substrate enhance the migration of La, Cr, or Ca atoms through the Pt electrode and increase the resistance of a heater. It is considered the increase of resistance is caused by such reaction.