New Luminescent Solids in the Ln−W(Mo)−Te−O−(Cl) Systems

Solid-state reactions of lanthanide(III) oxide (and/or lanthanide(III) oxychloride), MoO₃ (or WO₃), and TeO₂ at high temperature lead to eight new luminescent compounds with four different types of structures, namely, Ln₂(MoO₄)(Te₄O₁₀) (Ln = Pr, Nd), La₂(WO₄)(Te₃O₇)₂, Nd₂W₂Te₂O₁₃, and Ln₅(MO₄)(Te₅O₁₃)(TeO₃)₂Cl₃ (Ln = Pr, Nd; M = Mo, W). The structures of Ln₂(MoO₄)(Te₄O₁₀) (Ln = Pr, Nd) feature a 3D network in which the MoO₄ tetrahedra serve as bridges between two lanthanide(III) tellurite layers. La₂(WO₄)(Te₃O₇)₂ features a triple-layer structure built of a [La₂WO₄]⁴⁺ layer sandwiched between two Te₃O₇^2- anionic layers. The structure of Nd₂W₂Te₂O₁₃ is a 3D network in which the W₂O₁₀^8- dimers were inserted in the large tunnels of the neodymium(III) tellurites. The structures of Ln₅(MO₄)(Te₅O₁₃)(TeO₃)₂Cl₃ (Ln = Pr, Nd; M = Mo, W) feature a 3D network structure built of lanthanide(III) ions interconnected by bridging TeO₃^2-, Te₅O₁₃^6-, and Cl^- anions with the MO₄ (M = Mo, W) tetrahedra capping on both sides of the Ln₄ (Ln = Pr, Nd) clusters and the isolated Cl^- anions occupying the large apertures of the structure. Luminescent studies indicate that Pr₂(MoO₄)(Te₄O₁₀) and Pr₅(MO₄)(Te₅O₁₃)(TeO₃)₂Cl₃ (M = Mo, W) are able to emit blue, green, and red light, whereas Nd₂(MoO₄)(Te₄O₁₀), Nd₂W₂Te₂O₁₃, and Nd₅(MO₄)(Te₅O₁₃)(TeO₃)₂Cl₃ (M = Mo, W) exhibit strong emission bands in the near-IR region.