Low-temperature sintered Li2BaP2O7 ceramic: Structural insights, bond characteristics, and microwave dielectric properties

The Li 2 BaP 2 O 7 ceramics, synthesized through the solid-state reaction method, exhibit a pure monoclinic phase. Upon sintering at 750 °C, the ceramic achieves a high relative density of 97.3 %, which is indicative of an optimal microstructure conducive to the superior microwave dielectric properties: a ε r of 9.9, a Q × f of 86200 GHz, and a τ f of −95.4 ppm/°C. The variation in relative density is identified as the principal driver of changes in both the ε r and Q × f values for the Li 2 BaP 2 O 7 ceramics. The molecular polarizability is pivotal in determining the ε r of Li 2 BaP 2 O 7 ceramics. The P-V-L theory analysis elucidates that the P-O bond significantly surpasses other chemical bonds in contributing to the ionicity, lattice energy, and bond energy, thereby underscoring its dominance over the three principal microwave dielectric characteristics. Furthermore, Raman spectroscopy data demonstrate that the P-O bond vibration predominantly governs the overall vibrational spectrum.