Cd<sub>5</sub>Te<sub>4</sub>O<sub>12</sub>X<sub>2</sub> (X = Cl, Br, I): a new oxyhalide family with [CdO<sub>4</sub>X] mixed anionic units and adjustable optical properties.
Discover a new family of tellurate halides with adjustable optical properties! Cd5Te4O12X2 (X = Cl, Br, I) boasts a unique layered structure and impressive birefringence, paving the way for advanced optical applications.
This study reports the rational design and synthesis of three novel tellurate halides, Cd5Te4O12X2 (X = Cl, Br, I), using the flux method. The compounds crystallize in a layered 3D structure with pyramid-shaped [CdO4X], octahedral [CdO6], and triangular [TeO3] units. Notably, the optical properties can be tuned by varying the halide, with Cd5Te4O12Cl2 exhibiting a large birefringence of 0.113 at 1064 nm. Theoretical calculations suggest these are direct-bandgap materials, primarily determined by the mixed anionic units. This work expands the chemical and structural diversity of mixed anionic compounds, offering new insights for designing advanced optical materials.