Novel thermally stable, high quality factor Ba 4 (Pr 0.4 Sm 0.6 ) 28/3 Ti 18− y Ga 4 y /3 O 54 microwave dielectric ceramics

Abstract High dielectric constant Ba 4 (Pr 0.4 Sm 0.6 ) 28/3 Ti 18− y Ga 4 y /3 O 54 (BPSTG) (0 ≤ y ≤ 1) microwave ceramics with enhanced dielectric properties were synthesized via the traditional solid‐state processing for the first time. The crystal structure, microstructure, and microwave dielectric characteristics were investigated in details. X‐ray diffraction results showed that all well‐sintered samples belonged to a single tungsten bronze type phase. Results showed that partial substitution of Ga 3+ for Ti 4+ is an effective way in adjusting the temperature coefficient of resonant frequency (TCF) value of the Ba 4 (Pr 0.4 Sm 0.6 ) 28/3 Ti 18 O 54 ceramics and increased the quality factor (Qf) values. The variation tendency of dielectric constant was in accordance with the ionic polarizability. The Qf values highly depend on the grain size from the scanning electron microscopy results. A near zero TCF value can be obtained by carefully adjusting the substitution of Ga 3+ content. Infrared reflectivity (FIR) spectra were employed to reveal the relationship between the phonons and microwave dielectric properties. At last, excellent combinations dielectric properties of ε r = 78.5, Qf = 12,400 GHz, TCF = +2.1 ppm/°C were achieved in BPSTG ceramics when y = 0.75.