Phase equilibria in the ternary reciprocal system Li, Ba // BO₂, F and growth of bulk β-BaB₂O₄ crystals

In order to find the optimum solvent for the growth of nonlinear optical β-BaB₂O₄ crystals, the phase relationships in the ternary reciprocal system Li, Ba // BO₂, F have been studied using solid state synthesis, differential thermal analysis and X-ray powder diffraction. Isothermal and polythermal sections of the system Li, Ba // BO₂, F are reported. In the studied system, the following compounds are formed: LiBa₂B₅O₁₀ (melts by peritectic reaction at 930°C, i.e. 1203 K) and LiBaF₃ (melts incongruently at 850°C, i.e. 1123 K). Visual polythermal analysis of seeding and growth of β-BaB₂O₄ crystals in this system was carried out. The primary crystallization field of β-BaB₂O₄ was defined. Using the top-seeded pulling technique, a β-BaB₂O₄ crystal of 93 mm in diameter, 34 mm in height and 520 g in weight has been grown.