Crystal structure and dielectric properties of novel temperature-stable SrLn2O4 (Ln=Ho, Tm) microwave dielectric ceramic

In this paper, a comprehensive investigation was conducted to the factors affecting the crystal structure and microwave dielectric properties of the SrLn2O4 (Ln= Ho, Tm) ceramics. Rietveld refinement results of the XRD patterns conclude that SrLn2O4 (Ln= Ho, Tm) ceramics belong to orthorhombic system with Pnam symmetry. The effects of porosity, packing fraction and lattice energy on the properties of SrLn2O4 (Ln= Ho, Tm) ceramics were precisely analyzed. Excellent properties for SrTm2O4 ceramics (epsilon r = 14.49, Qxf = 41138 GHz, tau f = - 36.69 ppm/ degrees C) and SrHo2O4 ceramics (epsilon r = 14.87, Qxf = 24021 GHz, tau f = - 17.03 ppm/degrees C) can be achieved due to good densities and high packing fraction and lattice energy. In addition, CaTiO3 is proved to be well compatible with SrLn2O4 (Ln= Ho, Tm) ceramics. Near-zero tau f were obtained in SrTm2O4 + 1.8 wt% CaTiO3 ceramic and SrHo2O4 + 1.2 wt% CaTiO3 ceramic, making them ideal candidates for applications in microwave band.