Synthesis, microstructure, and dielectric properties of novel dual-phase high-entropy (Ba 0.2 Ca 0.2 Sr 0.2 Na 0.2 Bi 0.2 )WO 4 ceramics for LTCC applications

Novel dual -phase high -entropy (Ba 0.2 Sr 0.2 Ca 0.2 Na 0.2 Bi 0.2 )WO 4 ceramics were designed to reduce the sintering temperature and optimize the frequency - temperature coefficients of scheelite-type AWO 4 ceramics. XRD and Rietveld refinement analyses revealed that the ceramic contained dual phases of BaWO 4 and Na 0.5 Bi 0.5 WO 4 . The phases had a tetragonal structure with the I4 1 /a space group, as verified by TEM. With increasing sintering temperature, the epsilon r exhibited a decreasing trend owing to the combined influence of ionic polarizability and density. In addition, the variation trend of the Q x f value was similar to that of the density, and its intrinsic influence was investigated by analyzing the FWHM of the Raman vibrational peak. The tau f was well optimized and exhibited a variation trend similar to those of the lattice distortion and microstrain. Finally, the (Ba 0.2 Sr 0.2- Ca 0.2 Na 0.2 Bi 0.2 )WO 4 sintered at 950 degrees C had the outstanding properties: epsilon r of 13.8, Qxf of 33,110 GHz and tau f of -34 ppm/ degrees C at 9 GHz.