Phase composition, dielectric properties, bond characteristics, and Raman spectra of NaAg1-xBix/3MoO4 ceramics synthesized at ultra-low temperature

In this study, the NaAg 1-x Bi x/3 MoO 4 (x = 0.06, 0.12, 0.18, and 0.24) ceramics were successfully synthesized via solid-state reaction at 400–535 °C. Notably, the NaAg 0.82 Bi 0.06 MoO 4 ceramic exhibited exceptional dielectric properties at 450 °C (ε r  = 7.39 ± 0.05, Q × f = 18,867 ± 1480 GHz, τ f  = −84.8 ± 1.3 ppm/°C). The Rietveld refinement confirmed its spinel-like structure belonging to the Fd-3m (227) space group, along with the formation of a Na 0.5 Bi 0.5 MoO 4 secondary phase, as supported by SEM and EDS analyses. Further investigation revealed that the Na 0.5 Bi 0.5 MoO 4 phase adversely impacted the Q × f value, while the relative density positively correlated with Q × f. Based on the Shannon additivity rule, the contribution of Bi 3+ ions to ε r was elucidated. The P–V-L theory provided a theoretical foundation for understanding the dielectric behavior of NaAg 1-x Bi x/3 MoO 4 ceramics. Additionally, Raman spectroscopy directly confirmed the enhancement of molecular polarizability by Bi 3+ ions and disclosed a negative correlation between the A 1g vibration mode and Q × f, further elucidating the intimate link between internal lattice vibrations and microwave dielectric properties.