Elastic and Dielectric Properties of LiNbO₃

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Elastic constants C₁₁, C₃₃, C₄₄, and C₆₆, and dielectric susceptibilities χ₁₁ and χ₃₃ in LiNbO₃, were determined over the temperature range from 300 to above 1030 K. The elastic-constant difference between constant polarization and constant field C_ii^P−C_ii^E, and the inverse-susceptibility difference between constant strain and constant stress (χ_ii^x)⁻¹−(χ_ii^X)⁻¹ are interpreted in terms of both electrostrictive and higher-order interaction between strain and polarization. The results for χ₃₃ indicate that LiNbO₃ undergoes nearly second-order phase transition at T_C=1410 K. Above T_C, χ₃₃ showed dispersion in the frequency range between 1 and 13 MHz. A comparison of these results with soft-mode frequency implies that the soft mode couples with a low frequency relaxation process near T_C.