Te–Se replacement induced structural transition and enhanced band gaps in Cd 5 Se 4 O 12 Cl 2 and Cd 5 Se 4 O 12 Br 2

were determined to be 0.089 and 0.093@1064 nm. The results illustrate the feasibility of Te-Se substitution in the oxyhalide family and offer valuable insights for developing new oxyhalide-based functional materials with adjustable properties.