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Crystal growth methods that do not require high temperatures are highly needed for the facile growth of oxide single crystals with melting points of several thousand degrees Celsius. This paper represents the first report of a method for the low-temperature growth of ruby crystals (chromium-doped Al 2 O 3 ) at 750 °C, which is one-third of the conventionally required temperature (2050 °C). In solution-based crystal growth, the target crystal is grown at a temperature considerably lower than its melting point. However, conventional crystal growth processes involving solvent evaporation and cooling require high temperatures to completely liquefy the material, with previously reported solution growth temperatures of ≈1100 °C. Supersaturation based on the decomposition of crystal-solvent intermediates eliminates the need to completely liquefy the material, enabling low-temperature crystal growth. The combination of computational and experimental investigations helps determine the optimum conditions for low-temperature crystal growth. The proposed method is a novel green process that breaks the conventional frontiers of crystal growth while ensuring eco-friendliness and low energy consumption. In addition, its scope can potentially be expanded to the synthesis of various crystals and direct growth on substrates with low melting points., (© 2024 Wiley‐VCH GmbH.)

Chalcogenide-containing compounds have been widely studied as infrared nonlinear optical (NLO) materials. However, they have never been applied in the ultraviolet (UV) region owing to the high energy levels of chalcogen anions, leading to band gap narrowing. We report the synthesis of a new UV NLO oxysulfide La 3 Ga 3 Ge 2 S 3 O 10 with an exceptionally wide band gap of 4.70 eV due to from the unique anion-ordered frameworks comprising 1D 1 ∞ [(Ga 3/5 Ge 2/5 ) 3 S 3 O 3 ] triangular tubes and 0D (Ga 3/5 Ge 2/5 ) 2 O 7 dimers of corner-sharing (Ga/Ge)S 2 O 2 and (Ga/Ge)O 4 tetrahedra, respectively. Second harmonic generation (SHG) measurements revealed that La 3 Ga 3 Ge 2 S 3 O 10 was phase matchable with twice the SHG response of KH 2 PO 4 . The results of theoretical calculations suggest that the strong SHG response is mainly attributable to the S-3p and O-2p orbitals in the occupied states. The anion-directed band-gap engineering may give insights into the application of NLO oxychalcogenides in the UV regions., (© 2021 Wiley-VCH GmbH.)