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Red-light phosphor materials are crucial components in solid-state lighting (SSL) for simulating natural sunlight. Mn-doped Mg 2 TiO 4 is a promising fluoride-free redemitting phosphor; however, a sensitizer is necessary to enhance its brightness. In this work, we perform ab initio calculations based on the density functional theory (DFT) to systematically examine the electronic-band coupling between the luminescent center, Mn, and several possible sensitizers, Zn, Nb, Mo, In, Sn, and Ta. Nb was identified as the optimal sensitizer. Well-crystallized 0.1 at. % Mn and 0.0−0.7 at. % Nbcodoped Mg 2 TiO 4 were synthesized at 1450 °C. Synchrotronradiation-based X-ray absorption spectroscopy (XAS) experimentally validated the proposed atomistic structure, indicating that the Nb 5+ dopant substitutes Ti 4+ at the 16d sites, leading to the formation of Ti vacancies and of a parasitic MgTiO 3 phase. Effective sensitization, resulting in a 243% enhancement of the photoluminescence intensity, was achieved. The 0.1 at. % Mn and 0.5 at. % Nb-codoped Mg 2 TiO 4 were obtained as an ultrabright "rare-earth-free" (RE-free) and "fluoride-free" red-light phosphor.

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Single crystalline microcubes of a new tantalum compound, tantalum oxychloride (TaO2.18Cl0.64), have been fabricated hydrothermally in a concentrated aqueous solution of hydrochloric acid and acetic acid. They contain a superstructure and exhibit remarkably enhanced photocatalytic activities for hydrogen production due to the improved light harvest and facilitated charge transport.

Hydrothermal method was employed to prepare the flower-like hierarchical structures of F–Bi4TaO8Cl for photocatalytic hydrogen production under visible light irradiation.