Preparation and characteristics of YTiTaO₆ and YTiTaO₆:Er³⁺/Yb³⁺: Synthesis, aeschynite phase, and photoluminescence of YTiTaO₆

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Aeschynite-type fine crystals of YTiTaO₆ and Er³⁺- and Yb³⁺-co-doped YTiTaO₆ (YTiTaO₆:Er³⁺/Yb³⁺) were synthesized for the first time using hydrothermal method at 240 °C. The effects of Yb³⁺ and Er³⁺ concentrations and heating temperature in air on their crystalline phases were investigated. The images of transmission electron microscope (TEM) and energy dispersive X-ray spectrometry (EDS) elemental mapping showed that their metal cations were dispersed homogeneously in the cube-like crystals in the range of 200–300 nm. A single phase of aeschynite appeared in all of the as-prepared YTiTaO₆ and YTiTaO₆:Er³⁺/Yb³⁺ samples synthesized hydrothermally at 240 °C and samples after heating at 1100 and 1200 °C in air although YTiTaO₆ is known to possess euxenite-type structure. The lattice constants of the orthorhombic aeschynite phase decreased slightly according to the Vegard’s law as the concentration of Yb³⁺ was increased from y = 0 to 0.30 in the Er_0.10Yb_yY_0.90−yTiTaO₆ system. Under excitation at 270 nm the pure YTiTaO₆ showed light blue green and broadband photoluminescence centered at 520 nm. The aeschynite-to-euxenite phase transition occurred completely in the whole Yb³⁺ concentration range, y = 0–0.30 in Er_0.10Yb_yY_0.90−yTiTaO₆ and pure YTiTaO₆ as a consequence of heating at 1400 °C for 1 h in air.