Topology of liquidus surface in B2O3-Li2O·B2O3-Li2O·MoO3–MoO3 system: implications to the growth of lithium triborate single crystals

Abstract The paper presents the literature-based review of phase diagrams for the B 2 O 3 -Li 2 O, B 2 O 3 -MoO 3, LiO 2 -MoO 3 binary systems and B 2 O 3 -Li 2 O-MoO 3 ternary system and the results of the experimental studying the polythermal sections of Li 2 O·B 2 O 3 - Li 2 O·MoO 3, Li 2 O·3B 2 O 3 - MoO 3 and Li 2 O·3B 2 O 3 - 2Li 2 O·5MoO 3 systems. The section of Li 2 O·B 2 O 3 - Li 2 O·MoO 3 was confirmed to be quasi-binary: it divides the ternary phase diagram into two subsystem diagrams, which can be investigated independently. Basing on original and published data the topological analysis of liquidus surface in the B 2 O 3 - Li 2 O·B 2 O 3 - Li 2 O·MoO 3 subsystem –which is of special interest for the growth of lithium triborate (LBO) single crystals –was performed. Due to the lack of information several topologies of the surface may be provided which accord well with the available experimental data. It was shown that to choose a correct version of topology one could use the data on the subsolidus triangulation of the compositional tetragon of the subsystem under investigation. The relevant experiment was carried out and the triangulation scheme was determined through the phase composition of one sample. The topological scheme of liquidus surface and the subsolidus triangulation scheme in the compositional tetragon of the B 2 O 3 - Li 2 O·B 2 O 3 - Li 2 O·MoO 3 - MoO 3 subsystem were plotted. We succeeded to define the region of LBO primary crystallization on the phase diagram and to grow optically good-quality LBO single crystals.