Na3AEZn2B3O9 (AE = Mg, Ca): two new short-wave ultraviolet beryllium-free Sr2Be2B2O7-type zincoborates designed by chemical cosubstitution†
a
Jiang-Gao
Mao
*a
Abstract
Exploration of short-wave ultraviolet beryllium-free Sr2Be2B2O7-type borates is of great significance to the development of short-wave ultraviolet lasers. As a structural analogy to BeO4, the ZnO4 unit has been demonstrated as a facile building unit for the design of beryllium-free borates with balanced overall performance. Nevertheless, despite the discovery of numerous zincoborates, no Sr2Be2B2O7-type zincoborates with characteristic bilayer structures constituted by ZnO4 and BO3 units have been found, highlighting the great challenge in the design and syntheses of Sr2Be2B2O7-type zincoborates. Herein, two new beryllium-free Sr2Be2B2O7-type zincoborates, namely, Na3AEZn2B3O9 (AE = Mg and Ca), were rationally obtained by a chemical cosubstitution design strategy. With the cosubstitution of Sr2+, Be2+ and out-of-plane bridging O2− of {Sr[Be2(BO3)2O]}∞2− bilayers of Sr2Be2B2O7, Na3AEZn2B3O9 (AE = Mg and Ca) featuring a new Sr2Be2B2O7-type bilayer structure of {Na3[Zn2(BO3)2(BO3)]}∞2− were successfully isolated, indicating the feasibility of chemical cosubstitution for the design of Sr2Be2B2O7-type zincoborates. In particular, Na3CaZn2B3O9 exhibits a wide band gap of 4.43 eV, a moderate birefringence of 0.045@1064 nm and a high melting point of 843 °C, being favorable to practical applications.
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