Pressure induced structure distortion in ferroelectrics with high Curie point and enhanced piezoelectric properties

High-temperature ferroelectric materials perform piezoelectric properties at elevated temperature, and they could detect strains, vibrations, and noise under severe thermal conditions. Therefore, these materials could be widely applied in material processing, automotive, aerospace, and power industries. As the promising materials, perovskite-like layered (PL) structure ferroelectrics, like La2Ti2O7, were widely investigated due to their high Curie points (Tc > 1300°C). However, the low piezoelectric constants restricted the applications. Here, the high pressure treatment was surprisingly found to be an effective method to improve the piezoelectric/ferroelectric performances on bulk La2Ti2O7 ceramics. The high-pressure-treated La2Ti2O7 shows an enhanced piezoelectric constant by 74% compared to un-treated sample, which is the highest d33 achieved in PL-structure ferroelectrics with Tc > 1400°C. This is because the high-pressure sintering distorts the structures, increasing the spontaneous polarizations (Ps) and piezoelectric behaviors. These results offer a method to fabricate the bulk ceramics with strain/stress effect, and might be instructive for the materials design in the future.