Structure, dielectric, electrostrictive and electrocaloric properties of environmentally friendly Bi-substituted BCZT ferroelectric ceramics

In this study, environmentally friendly Bi-substituted [(Ba0.85Ca0.15)1-3x/2Bix](Zr0.1Ti0.9)O3 (BCZT-xBi) ferroelectric ceramics with x = 0-0.08 were prepared using a solid-state sintering method. The structures, dielectric, electrostrictive and electrocaloric properties of the Bi-substituted BCZT ceramics were thoroughly investigated. With an increase in the Bi3+ content, the temperature corresponding to the maximum permittivity (Tm) decreased monotonously. Meanwhile, the broadening of the dielectric peaks and the increase in the relaxation coefficient of the ceramics transformed their typical ferroelectric-to-paraelectric phase transition to diffuse phase transition (DPT). This was further confirmed by the trends shown by the ferroelectric properties of the ceramics. The current peak intensity in current-electric field (I-E) curves decreased with an increase in x and finally became constant, indicating that domain reversal disappeared gradually. High electrostrictive coefficient Q33 values of 0.0307, 0.0299 and 0.0223 m4/C2 were obtained for the ceramics with x = 0.02, 0.04 and 0.06 respectively. The Q33 values of the ceramics indicated their temperature-insensitive nature over the temperature range of 30-120 degrees C. Although the maximum value of the electrocaloric adiabatic temperature change (Delta T) (0.91 K) was achieved at x = 0.02, the thermally stability of Delta T is improved with an increase in x from 0.02 to 0.06. The results indicated that x = 0.06 improved the thermal stability of the electrostrictive and electrocaloric performance. By increasing the driving field strength, better electrostrictive and electrocaloric responses could be achieved.