Significantly improved dielectric and piezoelectric properties of BiAlO3 modified potassium bismuth titanate lead-free ceramics

The effects of BiAlO3 content on the crystal structure, microstructure, dielectric, and piezoelectric properties of (1-x)(K0.5Bi0.5)TiO3-xBiAlO(3) (abbreviated as KBT-BA) (x = 0-0.05) ceramics were systematically studied. Rietveld refinement of XRD data revealed a decrease in tetragonality and an increase in weight fraction of the cubic phase with the increase in BiAlO3 incorporation. The frequency-dependent temperature of dielectric maximum (T-m) was found to increase from 351 degrees C for pure KBT to 372 degrees C (at 1 MHz) for 1% BA doped unpoled sample. An increasingly diffuse dielectric anomaly and strengthening of relaxor behavior were noticed in KBT-BA solid-solution with the increase in BA content. Temperature dependence of DC conductivity followed Arrhenius behavior, and the activation energies were found to be in 0.98 +/- 0.03 eV to 1.18 +/- 0.02 eV range for all compositions. The piezoelectric charge coefficient (d(33)) was found to be 109 pC/N for 5% BiAlO3 doped sample, which is similar to 80% higher than that of pure KBT.