Bi(SO4)F<middle dot>H2O and Bi(SO4)(NO3)<middle dot>3H2O: Chemical Substitution-Induced Birefringence Enhancement in Bismuth Sulfates

초록

Two new Bi(III)-based sulfates, namely, Bi(SO4)F<middle dot>H2O (BSOF) and Bi(SO4)(NO3)<middle dot>3H(2)O (BSNO), have been successfully synthesized through aliovalent replacement of partial [SO4](2-) groups with F- and [NO3](-) anions, respectively, in the parent structure of Bi-2(SO4)(3). Such chemical replacement altered the coordination environment of Bi3+ cations, facilitating changes in the structure and optical properties. Notably, the birefringence values of BSOF and BSNO are found to be 4.4 and 15.5 times that of parent Bi-2(SO4)(3). Further investigation into the structure-property relationship revealed that the birefringence enhancement in BSOF and BSNO is attributed to the improvement of the polarizability anisotropy of Bi3+-centered polyhedra in BSOF and BSNO compared to that of Bi-2(SO4)(3). In addition, the existence and optimized arrangement of planar [NO3](-) groups are also indispensable for further birefringence improvement of the BSNO compound.

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