High-Performance [00l]-Textured BiAlO3-Doped K0.5Bi0.5TiO3 Ceramics

[00l] grain-oriented 0.95K0.5Bi0.5TiO3–0.05BiAlO3 (named K5BA-T) ceramics were prepared via the reactive template grain growth (RTGG) and tape casting technique. High-aspect-ratio K5BA powder was prepared using a plate-shape 4-layer aurivillius oxide (K0.5Bi4.5Ti4O15) powder as the template. The effects of grain morphology modification and texturing on the structural, dielectric, and piezoelectric properties of K5BA-T were systematically investigated. The average plate size of ∼6.5 μm with a thickness of ∼400 nm was observed in the K5BA sample. X-ray diffraction (XRD) and bulk texture measurements confirmed the texturing of K5BA-T in the [00l] crystallographic direction with a calculated Lotgering factor of ∼80%. Two anomalies in the temperature-dependent dielectric plot of the poled K5BA-T sample signified additional poling-induced phase transition. A lower value of room-temperature (RT) dielectric constant (εr) of ∼ 200 (at 1 MHz) and a higher piezoelectric charge coefficient (d33) of ∼145 pCN–1 were obtained in the poled K5BA-T ceramic compared to that of the 0.95K0.5Bi0.5TiO3–0.05BiAlO3 ceramic with randomly oriented grains (named K5BA-R). Consequently, the piezoelectric voltage coefficient (g33) estimated for the textured ceramic showed a 650% increment (g33 ∼ 80 × 10–3 V mN–1) over the K5BA-R sample (g33 ∼ 12.5 × 10–3 V mN–1). The transduction coefficient (d33·g33) of K5BA-T ceramic was calculated to be ∼11 600 × 10–15 m2 N–1, which is nearly 9 times higher compared to its random counterpart. Further, a piezodevice fabricated using poled ceramic for energy harvesting showed an output voltage of ∼7 V with a current response of ∼2 μA under normal finger-tapping motion.