Anisotropic precursor behavior in LiTaO3: Polar coherence at ultrahigh temperatures without ferroelasticity

We report the persistence of the converse piezoelectric effect to exceptionally high temperatures in ferroelectric congruent LiTaO3 single crystals. Resonant piezoelectric spectroscopy reveals a strong and stable piezoelectric response up to temperatures approaching the ferroelectric transition (Tc = 855 K), demonstrating remarkable thermal stability of the piezoelectric response. A finite electromechanical response persists up to the highest measurement temperature of 1050 K, whereas a pronounced enhancement develops below 915 K along the c-axis but is absent along the perpendicular direction. This anisotropic precursor enhancement develops in the absence of significant bulk elastic softening above Tc, distinguishing LiTaO3 from ferroelastic perovskites in which precursor behavior is accompanied by pronounced elastic anomalies. These observations demonstrate that coherent polar precursor behavior can persist to exceptionally high temperatures in a non-ferroelastic ferroelectric, considerably extending the experimentally established temperature range over which such behavior has been identified.