Poling procedures and piezoelectric response of (Ba_0.85Ca_0.15Zr_0.1T_0.9)O₃ ceramics

The goal of the current report was to find the optimal poling conditions: poling field, poling time and poling temperature for lead-free (Ba0.85Ca0.15Zr0.1T0.9)O3 ceramic. It has been noticed that the low poling field (< 2 kV/mm) was insufficient for obtaining ideal poling state (θ = 90°) due to the incomplete switching of domains and thus low piezoelectric properties (d33 ≤ 438 pC/N and kp ≤ 49%). However, relevance of higher poling voltage (> 2 kV/mm) may induce electric breakdown and physical defects such as cracks in the sample, which also leads degradation of piezoelectric properties. The optimal poling field, poling time and poling temperature was found to be 2 kV/mm, 10 min and 24°C, i.e., near room temperature, respectively to achieve nearly ideal poling state (θ = 86°) obtained by impedance spectra, and thus enhanced piezoelectric constant d33 = 505 pC/N and kp = 56% at room temperature. The O-T phase transition point was identified at 32.6°C, for which a peak value of d33(E=0V) = 622 pm/V was realized.