Thermally-stable high dielectric properties of (1–x)(0.65Bi _1.05 FeO ₃ –0.35BaTiO ₃ )–xBiGaO ₃ piezoceramics

The thermal stability of the dielectric behavior and the crystal structure, surface morphology, polarization, and piezoelectric properties of lead-free BiGaO ₃ (BG)-modified 0.65Bi _1.05 FeO ₃ –0.35BaTiO ₃ (abbreviated as BF–BT–xBG with 0 ≤ x ≤ 0.03) ceramics were investigated. XRD analysis of BF–BT–xBG dielectric ceramics revealed no remarkable change in the crystal structure within the studied composition range. Around the critical composition (BF–BT–0.02BG), the piezoelectric constant (d ₃₃ ) and electromechanical coupling factor (k _p ) reached maximum values of ⁓205 pC/N and 34.5%, respectively. The BF–BT–BG dielectric system also exhibited a thermally-stable ε _r (801–902, at 30 °C – 500 °C), high T _max (395 °C – 416 °C), colossal ε _rmax (46,363–76,303), and ε _rmid (2241 ± 15%–3678 ± 15%, with tanδ ≤ 0.08) across a wide temperature range of 198 °C–332 °C. This improvement in the dielectric properties and high T _max of the optimum specimen can be attributed to the BiGaO ₃ -modification and quenching process, which made the system viable for applications that require high-temperature dielectric stability.