Piezoelectric effect in the LaBGeO$_5$ ferroelectric crystal

Room-temperature piezoelectric moduli of a new high-temperature ferroelectric crystal, LaBGeO$_5$(LBGO), are for the first time determined experimentally. It is shown that the piezoactivity of this crystal is close to that of quartz. Comparative analysis of temperature dependences of spontaneous polarization and spontaneous deformation was carried out, and the piezomoduli were measured at room temperature. Based on these data, it was shown that this crystal, which undergoes the change of symmetry 32 → 3 during the phase transition ($T_c=533^{\circ}$C), is not a multiferroelectric. Its “transient” piezomoduli should not undergo noticeable anomalies at the Curie point, and the dependence d 3i ∼ (T c − T)−1/2, which is common for uniaxial ferroelectrics, is expected for morphic piezomoduli associated with polarization along axis 3.