Investigation of the structural characteristics, dielectric properties, and infrared reflectivity spectra of AlON transparent ceramics

Al(8+x)/3O4−xNx (x = 0.299–0.575) transparent ceramics were fabricated by presintering and subsequent hot isostatic pressing (HIP) technology. The XRD and SEAD analyses verified that a complete solid solution with a cubic spinel structure was achieved in the entire composition range. The SEM characterization confirmed that the x = 0.299−0.510 samples are highly dense with rare residual pores, which was further demonstrated by HRTEM observations. In combination with phonon modes extracted by far-infrared reflectivity spectra, the intrinsic dielectric properties of AlON ceramics were estimated, which were consistent with the experimental results, revealing that the contribution to dielectric properties is dominated by the absorption of structural phonons. Moreover, as the nitrogen content increased, the measured permittivity (εr) of the samples was found to gradually increase from 9.41 to 9.68 at 7 GHz, while the quality factor (Q × f) values fluctuated from 43,750 to 76,923 GHz. Accordingly, the reported AlON transparent ceramics with exceptional dielectric performances are promising candidates for high-frequency 5 G applications.