K2RbB8PO16: A Borophosphate with Moderate Birefringence and Deep-Ultraviolet Transmission.

ABSTRACT

A new borophosphate, K2RbB8PO16 (KRBPO) was synthesized. It exhibits a bilayer structure consisting of two B-O layers with an 18-membered ring (18-MR) joined by [PO4], which is composed of the π-conjugated group [BO3] and non-π-conjugated groups [BO4] and [PO4]. The UV-vis-NIR diffuse reflectance spectroscopy shows that the cutoff edge is less than 200 nm. The calculation indicates that KRBPO exhibits moderate birefringence of 0.057@1064 nm, and the source of birefringence is mainly from the [BO3] groups.