Pb3Ba3Zn6(BO3)8 and α-BaZn2(BO3)2: new members of the zincoborates containing two different dimensional Zn–O units

Abstract

Two new zincoborates, namely, Pb₃Ba₃Zn₆(BO₃)₈ and α-BaZn₂(BO₃)₂, were synthesized by the high-temperature solution method and their structures were determined by single-crystal X-ray diffraction for the first time. The structure of Pb₃Ba₃Zn₆(BO₃)₈ can be described as a three-dimensional framework consisting of [Zn₄B₂O₁₅]_∞ chains and isolated ZnO₄ tetrahedra and BO₃ triangles, which contains three different types of tunnels with Pb²⁺ and Ba²⁺ cations residing among them. α-BaZn₂(BO₃)₂ exhibits a two-dimensional layered structure with a [Zn₂B₂O₆] layer, which is formed by [ZnBO₄] chains and [Zn₂B₂O₈] chains. Interestingly, both Pb₃Ba₃Zn₆(BO₃)₈ and α-BaZn₂(BO₃)₂ both contain two different dimensional Zn–O configurations in their structures, which has not been found in other zincoborates. In addition, thermal property analysis, and UV-vis-NIR diffuse reflectance and infrared spectroscopy were also performed. First-principles theoretical studies were also conducted to aid the understanding of their band structures and densities of states.