Polymorphic Smooth Interfaces Formation Based on the Biphasic BaTeMo2O9 Using Top Multi-Seeded Growth

An interesting phenomenon of two polymorphic heterojunctions is reported in this paper. The selective growth of the individual phases of high-quality α- and β-BaTeMo2O9 (BTM) crystals was successfully achieved using an optimized flux system and growth parameters. A biphasic BTM crystal based on a multiseeding technique used to control the nucleation and subsequent growth was realized in a one-flux system. The formation of a grain boundary, similar to a heterojunction, between the α- and β-BTM crystals emerged as an unavoidable consequence of this process, and the factors that led to the formation of the grain boundaries in the multiseeds were examined. Lattice mismatch and interfacial binding energy calculation verified that the BTM crystals were grown together rather than being physically adhered, and the chains at the grain boundary were linked by O5Mo–O–MoO5 dioctahedrons corner-sharing O atoms at the eutectic boundary. The screw dislocation growth mechanism was confirmed for β-BTM with the growth unit of a single cell, as well as the similarities in structures for both phases. Additionally, a “pseudo-liquid-phase epitaxial” growth model was used to describe the formation mechanism of biphasic BTM based on a “virtual supercell” of β-BTM. The successful implementation of polymorphic BTM growth may provide information regarding polymorph control, and the heterojunction between the two polymorphic phases may demonstrate interesting future applications.