Cryogenic transverse and shear mode properties of (1 - X)Pb(Mg _1/3Nb_2/3)O₃-xPbTiO₃ single crystal with the optimal crystallographic direction

The cryogenic transverse extensional and thickness shear properties of the (1 - x)Pb(Mg_1/3Nb_2/3)O₃-xPbTiO₃ (PMN-xPT) single crystal with the optimal crystallographic directions were investigated in present work. With the temperature down to 78 K, a characteristic decrease in piezoelectric strain constants (d₃₁, 2020-831 pC N^-1 and d₁₅, 4114-2823 pC N^-1) and compliance coefficients (s11E, 95.3-50.6 × 10^-12 m² N^-1 and s55E, 227-184 × 10^-12 m² N ^-1) was demonstrated. In comparison, the piezoelectric voltage constant (g₃₁ and g₁₅) and electromechanical coupling coefficient (k₃₁ and k₁₅) exhibits an almost temperature-independent behavior. Even at 78 K, high values of g₃₁ ∼ 0.045 Vm N^-1, g₁₅ ∼ 0.057 Vm N^-1, k₃₁ ∼ 0.86, and k₁₅ ∼ 0.94 can be obtained. Such superior low temperature piezoelectric performance is favorable for the cryogenic device designs and applications, especially for the hydrophones with high g_ij needed.