Variable Thermal Emittance Radiator Using Metal-Insulator Phase Transition in La1-xSrxMnO3

Abstract

A variable-emittance radiator device, made of thin and light ceramic tiles, has been developed for thermal control applications on spacecraft. The ceramic material used is La1-xSrxMnO3 with a perovskite structure, and shows a phase transition from ferromagnetic metal to paramagnetic insulator at around 290 K (Tc). This device automatically controls a spacecraft's temperature without electrical or mechanical instruments. Below the Tc, the device is metallic with a low thermal emittance of 0.3, and above the Tc, it becomes insulative with a high thermal emittance of 0.7. For the ceramic tiles, two different fabrication processes were studied to reduce the cost and weight; one is a conventional ceramic wafer process and the other is a thick film process on zirconia substrates. Total thickness of the ceramic tiles obtained is less than 70 µm and the weight is 450 gr/m2.