New Polymorphism for Ba3Zn2(BO3)3F with Two Polymorphs Exhibiting Anomalous Phase Transition

A new polymorph of Ba3Zn2(BO3)(3)F, alpha-Ba3Zn2(BO3)(3)F, was synthesized and its structure was determined by single crystal X-ray diffraction. The two polymorphous phases of Ba3Zn2(BO3)(3)F are referred to as alpha- and beta-Ba3Zn2(BO3)(3)F according to their synthesis temperature from low to high. Both structures exhibit a similar three-dimensional (3D) framework, while the two-dimensional (2D) (2)(infinity)[Zn2B2O7] layers in their structures show different configurations and feature diverse topological structures. Interestingly, an anomalous phase transition, that is, the high-temperature beta-phase having a higher density, was observed and further confirmed by detailed structural analyses, which shows that the unusual density evolution mainly originates from the different configurations of (2)(infinity)[Zn2B2O7] layers. Moreover, the phase transformation was characterized by powder X-ray diffraction (PXRD) and differential scanning calorimetry (DSC) analyses.

Automated summary

A new polymorph of Ba3Zn2(BO3)(3)F, alpha-Ba3Zn2(BO3)(3)F, was synthesized and studied for its structural properties, including an anomalous phase transition with different densities in the two polymorphous phases. This was confirmed by detailed structural analyses using powder X-ray diffraction and differential scanning calorimetry.