Crystal structure and microwave dielectric properties of BaZnP2O7-based ceramics with Sr2+ substitution

In this study, Ba1-xSrxZnP2O7 (0 ≤ x ≤ 0.1) ceramics were synthesized at 875–950 °C. The X-ray diffraction and SEM test revealed that Ba1-xSrxZnP2O7 (0 ≤ x ≤ 0.1) ceramics formed a single phase with a P-1 triclinic structure. Moreover, a moderate substitution of Sr2+ is conducive to grain growth and pore reduction. The εr value was primarily affected by the average bond ionicity (Afi) and porosity, while the unit molecule polarizability contribution was insignificant. The Q × f value was closely related to the packing fraction, Utotal, and FWHM value of the strongest peak with a wavelength of approximately 1050 cm−1 in Raman spectra. Additionally, the P–O bond significantly influenced the bond ionicity and lattice energy. The Ba0.92Sr0.08ZnP2O7 ceramic sintered at 925 °C for 4 h exhibits satisfactory microwave performance: εr = 8.26 ± 0.06, Q × f = 61,677 ± 1781 GHz, τf = −18.34 ± 0.21 ppm/°C.