Variable thermal emittance radiator using metal-insulator phase transition in La1-xSrMnO3

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 (T-c). This device automatically controls a spacecraft's temperature without electrical or mechanical instruments. Below the T-c, the device is metallic with a low thermal emittance of 0.3, and above the T-c, 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 mum and the weight is 450 gr/m(2).