Tailoring UV waveplate materials via rational assembly of functional motifs in scandium fluoride phosphate.

A novel fluorinated rare-earth phosphate, K₄NaScP₂O₈F₂, was identified, featuring a unique 0D structure. It exhibits high thermal stability, a short UV cutoff around 201 nm, and a low birefringence of 0.008 at 1064 nm, lower than those of most rare-earth phosphates. These attributes position K₄NaScP₂O₈F₂ as a promising candidate for waveplate crystals.