Direct Formation of Luminescent Fine Crystals Based on (Y,Eu)TiNbO₆ Complete Solid Solution with High Crystallinity

Abstract

Luminescent fine crystals of Y1.00−xEuxTiNbO6, x = 0–1.00 with high crystallinity were directly synthesized by mild hydrothermal method from weakly basic precursor solution mixtures of YCl3, EuCl3, TiOSO4, and NbCl5. Orthorhombic aeschynite‐type crystals in the range of 0.5–2.0 μm consisting of crystallites with 33–91 nm based on a complete solid solution in the YTiNbO6–EuTiNbO6 system were hydrothermally formed at 240°C for 5 h. A single phase of as‐prepared aeschynite‐type structure was maintained in all the (Y,Eu)TiNbO6 solid solution after heating at temperatures up to 1000°C for 1 h in air. In the range of composition x ≤ 0.6, the as‐prepared aeschynite‐type (Y,Eu)TiNbO6 solid solutions transformed to a single phase of euxenite structure after heat treatment at temperatures higher than 1100°C–1200°C. The as‐prepared (Y,Eu)TiNbO6 fine crystals in the range of composition x = 0.75–0.90 showed the strongest luminescence in the red spectral region: strong red (5D0→7F2 transition of Eu3+) and weak orange light (5D0→7F1) line spectra among the as‐prepared and heat‐treated samples. Another wet chemical synthesis route confirmed the advantage in directly synthesizing the (Y,Eu)TiNbO6 crystals through this hydrothermal method because heating at 1200°C for 1 h in air was necessary for obtaining crystalline (Y,Eu)TiNbO6 with sufficient luminescence intensity in a composition Y0.70Eu0.30TiNbO6 from amorphous powders that were formed via co‐precipitation method.

Hydrothermal synthesis of luminescent niobate thin rods

“…In order to improve the performance and properties of inorganic materials, the investigation on their synthesis techniques is an efficient way. 15), 16) Therefore, various investigations on the preparation of CaNb 2 O 6 using solidstate reaction, 4),7), 12) flux growth, 17) laser-heated pedestal growth, 10) glycothermal, 18) solgel, 19) and coprecipitation method 20) have been carried out. In recent years, from a viewpoint of green processing, great attention has also been devoted to a direct synthesis of fine inorganic materials at low temperatures.…”

Hydrothermal formation and up‐conversion luminescence of Er3+‐doped GdNbO4

“…In general, for refractory oxide materials in the multi‐component system, the building up processes including aqueous solution routes based on the reaction in the presence of liquid phases can attain the formation of more homogeneous nanocrystalline materials at lower temperatures than the cases based on the solid‐state reactions and breakdown processes. The hydrothermal synthesis method is well known to be able to synthesize homogeneous nanometer‐sized crystalline particles, and useful for the preparation of new compounds, metastable phases, solid solutions, and composite nanoparticles . Although a considerable number of studies have been made on the synthesis and investigation of up‐converting materials, there are only few studies on the preparation and properties of up‐converting GdNbO 4 doped with Er 3+ through hydrothermal route.…”