Doping level effects in Gd/Cr co-doped Bi3TiNbO9 Aurivillius-type ceramics with improved electrical properties

In this work, different amount of Cr2O3 (x = 0–0.3 wt%) as dopant were doped into the Aurivillius-type compound Bi2.8Gd0.2TiNbO9 (BGTN), such a kind of Gd/Cr co-doped Bi3TiNbO9 ceramics with improved electrical properties were synthesized by the convenient solid-state reaction route. The substitution of Cr3+ for Ti4+ at B-site induced the lattice distortion of pseduo-perovskite layer. Fewer Cr2O3 dopant (x<0.2) resulted in the grain refinement of ceramics. After Cr2O3 was added into BGTN, TC decreased to the vicinity of 908 °C. Below TC, the relaxed dielectric response resulted from charge carriers hopping induced another board dielectric permittivity peak, whose starting temperature shifts toward lower side gradually with increase of x. The values of Eacon calculated from the Arrhenius relationship between conductivity and temperature indicated the intrinsic conduction at high temperature is dominated by the long-range migration of doubly ionized oxygen vacancies. Moderate Cr2O3 dopant (x = 0.1–0.25) are conducive to the enhancement of piezoelectric property and thermal stability. The sample with x = 0.2 achieved both a high TC∼903 °C and a high d33∼18 pC/N at the same time. Also, its d33 can retain 80% of the initial value after the sample was annealed at 800 °C for 4 h.