Elastic and Thermoelastic Properties of the Twinned Perovskite LaGaO3 and the Cubic Untwinned Perovskite La0.294Sr0.706Al0.647Ta0.353O3

The elastic and thermoelastic constants of twinned crystals of LaGaO3 and untwinned crystals of La0.294Sr0.706Al0.647Ta0.353O3 have been measured by ultrasonic resonance methods. Both materials exhibit a quite similar elastic behaviour characteristic, as for perovskites. Employing a simple formula for ionic crystals, the elastic constants of both oxygen perovskites reveal a depression of about one third in comparison to the fluor perovskite LiBaF3.