The dielectric and microwave absorption properties variation with temperature of La0.5Sr0.5CoO3 ceramics and improved microwave absorption by FSS

Abstract

The dielectric and microwave absorption properties variation with temperature of La0·5Sr0·5CoO3 ceramics is studied in order to develop a kind of microwave absorbing material that can be used at 500 °C. La0.5Sr0.5CoO3 powder was prepared by solid state reaction method, the phase composition, microstructure and specific surface area in X and Ku bands before and after sintering at 500 °C for 100 h were analyzed. The powder shows perovskite structure and the abovementioned characteristics of the powder remain stable after the sintering. La0.5Sr0.5CoO3/paraffin samples were prepared to study the dielectric properties at room temperature. Generally, both the real and imaginary parts of the complex permittivity increase as the La0·5Sr0·5CoO3 content increases. La0.5Sr0.5CoO3/Al2O3 ceramic sheets were prepared by plasma spraying process and used for dielectric properties study from 100 °C to 500 °C. Then the microwave absorption properties at different temperatures were calculated from electromagnetic parameters according to the transmission line theory. When the temperature is 500 °C and the thickness is 1.5 mm, the La0·5Sr0·5CoO3/Al2O3 ceramic shows a good microwave absorption property in Ku band for the average reflection loss is −5.97 dB and the reflection loss is below −5dB in Ku band. Frequency selective surfaces (FSS) is designed to improve microwave absorption of La0·5Sr0·5CoO3/Al2O3 ceramic in 500 °C. The optimized reflection loss is below −10dB throughout X band with square periodic structure (C = 11.14 mm, a = 3.06 mm and t = 1.71 mm) or circular periodic structure (C = 13.32 mm, a = 1.88 mm and t = 1.82 mm).