Microwave absorption and infrared performance of Sm_0.5Sr _0.5Co_1-xNi_xO₃ (0 ≤ x ≤ 1.0) with the K₂NiF₄ structure

Sm_0.5Sr_0.5Co_1-xNi_xO₃ (0 ≤ x ≤ 1.0, SSCN, in short) with a K₂NiF₄ structure has been successfully prepared by a conventional solid-state reaction as a microwave absorber. The effects of Ni incorporation on the structure, electrical conductivity, infrared emissivity and microwave-absorbing properties are investigated in detail. XRD results show that the spinel structure is preferred to the perovskite structure for Ni-containing compounds. The infrared spectra of K₂NiF₄-type nickelates are recorded and discussed on the basis of their structural peculiarities. The Ni doping concentration could contribute to the decrease of electrical conductivity; in contrast, the infrared emissivity is increased. Moreover, microwave-absorbing properties in the frequency range 2-18 GHz at room temperature are sensitive to the Ni content. The complex permittivity, complex permeability and electromagnetic loss tangent have a sudden step change at a certain frequency. An optimal reflection loss of -14.5 dB is reached at 13.1 GHz with a matching thickness of 2 mm.