BaTi(BO3)2: an excellent birefringent material with highly coplanar isolated [BO3] groups

Abstract
A material with a large birefringence is needed for optical systems, and borate is a good choice as an excellent birefringent material. Herein, we report two borates BaMIV(BO3)2 (MIV = Ti, Sn), in which the [TiO6] and [SnO6] units have similar coordination environments. Moreover, the experimental birefringence of BaTi(BO3)2 is equal to or larger than 0.169 at 546 nm measured by using a polarizing microscope, which mainly originates from the high-density and parallel arrangement of the isolated [BO3] groups. This discovery indicates that BaTi(BO3)2 can be a promising ultraviolet birefringent material.
Funding Information
  • National Natural Science Foundation of China (U2003131, 61835014, 51972336)
  • Chinese Academy of Sciences (2020-XBQNXZ-002, GJJSTD20200007, KFJ-STS-QYZD-130, QYZDB-SSW-JSC049)
  • Natural Science Foundation of Xinjiang Province (2019D01A93)