Greatly Enhancing Birefringence of Fluosilicate through the Synergy Effect of Functional Units

Abstract

Short-wave ultraviolet optical crystals are widely used in various fields. Exploring organic-inorganic hybrid compounds is an effective approach for discovering crystal materials simultaneously possessing large band gap and birefringence. In this work, two novel organic-inorganic hybrid fluorosilicates, (C2H7N4O)2SiF6 and (C2H4N4)4ZnSiF6·H2O were obtained. (C2H7N4O)2SiF6 has the largest band gap among organic-inorganic hybrid fluorosilicates and unique [(C2H7N4O)2SiF6]∞ layered structure. (C2H4N4)4ZnSiF6·H2O has the largest birefringence (0.282@0.546 μm) among reported organic-inorganic hybrid fluorosilicates. In addition, we systematically analyze the structural and optical properties transformation from (C2H7N4O)2SiF6 to (C2H4N4)4ZnSiF6·H2O.