Ca, Sr を置換した LaCrO_3 薄膜高温発熱体の開発と評価

概要

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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,Sr), which is deposited on silicon and alumina substrates by RF magnetron sputtering and evaluate their characteristics. Thin films of Sr doped LaCrO3 deposited on alumina substrate orient in the (220) or (004) direction contrary to Ca doped LaCrO3. The resistance of thin films of LaCrO3 decreases with increasing content of Ca or Sr. At the same Ca or Sr mixing ratio, the resistance of Ca doped thin LaCrO3 films is smaller than that of Sr doped LaCrO3. Degradation of heating characteristics due to the dc current drive may be mainly evaporation of component such as Cr2O3 from the junction of thin film and cathode electrode. On the other hand, with heating by ac current drive, the degree of the degradation is much smaller. Thin film heaters exhibit uniform heating characteristic. A maximum heating temperature over 1300°C is achieved.
2004-02-01