Text this: Y<sub>5</sub>F<sub>3</sub>[AsO<sub>3</sub>]<sub>4</sub> and Y<sub>5</sub>Cl<sub>3</sub>[AsO<sub>3</sub>]<sub>4</sub>: Two Non-Isostructural Yttrium Halide Oxoarsenates(III) and Their Potential as Hosts for Luminescent Eu<sup>3+</sup>- and Tb<sup>3+</sup>-Doping
