Ultra-high piezoelectric properties and ultra-high Curie temperature of Li/Ce-doped La2Ti2O7 ceramics

The demand for ultra-high-temperature piezoelectric sensors in industrial applications has witnessed a rapid upsurge. In this study, the piezoelectric properties of La₂Ti₂O₇ (LTO) piezoelectric ceramics with a perovskite-like layered structure were enhanced by doping with Li/Ce ions. It was found that a remarkable 300% enhancement in the piezoelectric constant (d₃₃) value was achieved in Li/Ce-doped LTO ceramics compared to their pristine counterparts, reaching 6.4 pC N^-1 at room temperature with an ultra-high Curie temperature of 1408 °C. After annealing at 500 °C, the d₃₃ value of the samples can be further improved to 7.4 pC N^-1. Moreover, temperature-dependent resistivity measurements indicate that even at 1000 °C, the ceramics exhibit a high resistivity of 8.9 × 10⁵ Ω cm. By combining X-ray diffraction, Raman spectra, transmission electron microscopy and piezoresponse force microscopy data, the enhanced piezoelectricity of the ceramics is attributed to local heterogeneity induced by Li/Ce doping. Our results unequivocally demonstrate the suitability of modified LTO ceramics for ultra-high-temperature piezoelectric applications.