Experimental study demonstrates linear shifts in Curie temperature and birefringence across lithium metatantalate melt compositions, highlighting stoichiometry-dependent optical properties.
The ferroelectric Curie temperature of lithium metatantalate is linearly dependent on the melt stoichiometry. Curie temperatures ranging from 700° to 540°C were measured on single crystals and correspond to a melt composition variation of approximately 6 mole % on each side of apparent stoichiometry. High Curie temperatures occur at high lithium oxide concentrations. The Curie temperature of LiTaO 3 grown from a nominally stoichiometric melt is 618°± 5°C. The birefringence of lithium metatantalate is also a linear function of the melt composition. Birefringence values from +0.006 to –0.004 were measured and correspond to the melt composition variation described above with positive birefringence associated with low Curie temperatures.
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Ballman et al. (1967) studied this question.