Research of piezoelectric resonance in stoichiometric LiNbO$_3$ crystals in the high temperature and conductivity area

In order to establish conditions of lithium niobate based piezoelectric resonators application at high temperatures and high conductivity in a wide range of temperatures ($\sim$300 – 850K) we have researched piezoelectric, ferroelectric, dielectric properties and ion conductivity of near-stoichiometric LiNbO$_{3_{\operatorname{stoich}}}$ crystals. We have revealed that piezo-resonance is observed in LiNbO$_{3_{\operatorname{stoich}}}$ in a certain temperature range $\Delta T$ (correspondingly, in certain static conductivity relaxation time $\Delta\tau_V$ range) and frequencies range $\Delta\omega_R$ provided that $\tau_V^{-1}\ll\omega_{R}$. Such patterns are probably applicable not only to LiNbO$_{3_{\operatorname{stoich}}}$ crystals, but also to other piezoelectric materials.