Macroscopic Orientation Domains Grown via Aerodynamic Levitation: A Path toward Single Crystals

Abstract

Powder pellets of ca. 30 mg with the mol% composition 0.61Ga2O30.39La2O3 are levitated in a gas stream and melted using a pair of CO2 lasers. The levitating melt droplets crystallize to form La2Ga3O7.5 or LaGaO3 after the lasers are turned off. The microstructure of cross sections prepared from them is analyzed using scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD).One of the beads containing La2Ga3O7.5 shows a fully crystallized, polycrystalline microstructure while the other broke apart during cooling and its cross section shows only a single orientation domain which is more than 7 mm 2 in area. Solid-state 71 Ga NMR spectroscopy was applied to this sample and showed that it was not a single crystal but contains 2 only about 3 orientation domains. The bead containing LaGaO3 showed dendritic growth originating from multiple nuclei.Although a single crystal was not achieved by the applied experiments so far, a detailed correlation of measured cooling curves with the observed microstructures enables to devise steps along the path towards single crystal production in future experiments.

Crystallization of glass materials into transparent optical ceramics

“…The last two reported ceramics demonstrated once again the chemical and structural diversity of the fully crystalline ceramic materials that can be obtained via the ADL technique. Moreover, Wisniewski et al [133] tried to elucidate the growth mechanism in the La 2 Ga 3 O 7.5 glass-ceramic beads obtained via the ADL method in a search for the link between the experimental conditions during crystallization (e.g. cooling profiles) and the material's transparency, which could potentially enable fabrication of single crystals of metastable phases using this novel technique.…”

“…Moreover, recent advancements in the 3-D printing technology of both glass and ceramic transparent materials provided strong arguments for considering this technology for the fabrication of glass crystallized ceramics with high optical qualities. However, significant leap forward in glass crystallization technique would be provided by the development of single-crystal materials starting from the glass, as discussed in [133], which would open a door to a whole new field and unlock numerous application possibilities. However, another important point to reflect on is the potential for mass production and the applicability of transparent ceramics obtained via full glass crystallization.…”