Sn2PO4I: An Excellent Birefringent Material with Giant Optical Anisotropy in Non π-Conjugated Phosphate

Exploring non pi-conjugated phosphate birefringent crystal with a large birefringence has been a great challenge. Herein, based on the unique two-dimensional layered structure in KBe2BO3F2 (KBBF), two new compounds, Sn2PO4I and Sn2BO3I, were designed and synthesized successfully, maintaining the layer structural feature and enhancing the optical anisotropy of crystals. In particular, the birefringence of Sn2PO4I is larger than or equal to 0.664 @546 nm, which is largest among the reported borates and phosphates, even surpassing commercial birefringent crystals YVO4 and TiO2. This work indicates that a breakthrough in birefringence of inorganic compound was achieved. Also, it provides a guiding idea for exploring large birefringence materials in the future.

Automated summary

This study successfully synthesized two new compounds with large birefringence, especially Sn2PO4I, showing greater birefringence than other borates and phosphates, even surpassing commercial crystals. This breakthrough in inorganic compound birefringence provides a new direction for future exploration of materials with high birefringence.