Infrared Emissivities and Microwave Absorption Properties of Perovskite La_1-xCa_xMnO₃ (0≤x≤0.5)

Abstract:

La_1-xCa_xMnO₃(0≤x≤0.5) with perovskite-type structure has been successfully prepared by sol-gel method as a microwave and infrared multi-functional material. The effects of Ca incorporation on the stucture, electrical conductivity, infrared emissivity and microwave-absorbing properties were investigated in detail by XRD, 4-point probes resistivity measurement system,IR-2 infrared-emissivity analyzer and vector network analyzer. XRD results show that the perovskite structure of LaMnO₃ is hardly changed when the doping concentration (x) of Ca²⁺ is less than or equal to 0.5. The incorporation of Ca in LaMnO₃ leads to the decrease of electrical conductivity, while the infrared emissivities are decreased. Moreover, microwave-absorbing properties in the frequency range of 2-18 GHz are sensitive to Ca content. The optimal reflection loss calculated from the measured permittivity and permeability is 42 dB at 10.5 GHz with a thickness of 2.0 mm when the doping amount of Ca²⁺ is 0.1. It is possible to make Ca-doped lanthanum manganites achieve compatible camouflage capability for radar and infrared wave-band.