“…However, a number of procedures were developed to obtain the stoichiometric crystal. With regard to single-crystal growth, Kitamura et al [3] have modified the Czochralski method by the double-crucible method in order to obtain the stoichiometric crystal, but with this method the crystal obtained does not seem to be stoichiometric. Another bulk method [4] is using the addition of potassium to the congruent melt, in which the incorporation of potassium to the crystal was reported to be negligible.…”