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Differential calorimetry of lithium niobate single crystals

We conducted a series of calorimetric experiments with nominally pure lithium niobate single crystals of congruent composition from different manufacturers and with different cuts, the samples were exposed to temperatures of up to 1100 ℃. For all samples, a temperature feature is observed in the range of 800–900 °C, regardless of their crystallographic orientation. The calculated activation energy of about 150 kJ/mol indicates the diffusion mechanism of the transformation, most likely associated with the high mobility of lithium and niobium ions as well as the possibility of formation of oxygen vacancies in the crystal lattice of lithium niobate. In some cases, this technique can serve as a technological parameter for the manufacture of lithium niobate crystals of optical quality.