Fabrication and evaluation of Ca, Sr-doped-LaCrO3 thin film electric heaters

Abstract

Thin film heaters made of Sr- or Ca-doped lanthanum chromite (LaCrO 3) are fabricated by RF magnetron sputtering. Thin films of Sr-doped LaCrO3 deposited on alumina substrates are found to orient in the (220) or (004) direction, unlike Ca-doped films. The resistance of the films decreased with increasing concentration of Ca or Sr. At the same mixing ratio of Ca or Sr, the resistance of Ca-doped thin films was lower than that of Sr-doped films. Heating characteristics were affected by the purity of the alumina substrate. For dc constant-current drive, heating temperature increased with increasing heating time due to the increase in resistance. From the results of compositional analysis, the main factor in the degradation of heating characteristics upon applying dc drive may be the evaporation of components such as Cr2O3 at the junction of the thin film and the cathode. With ac drive, degradation did not occur. Thin film heaters exhibited uniform heating. A maximum heating temperature of over 1300°C was achieved.