PbCd2B6O12 and EuZnB5O10: syntheses, crystal structures and characterizations of two new mixed metal borates

Abstract

Two new mixed metal borates, namely, PbCd₂B₆O₁₂ and EuZnB₅O₁₀, have been synthesized successfully by high-temperature solid state reactions in platinum crucibles. Both compounds crystallize in the monoclinic space group P2₁/n. The structure of PbCd₂B₆O₁₂ features a novel 3D framework of [Cd₂B₆O₁₂]²⁻ composed of [(B₆O₁₂)⁶⁻]_n layers parallel to the ab plane, dimers of edge-sharing Cd(1)O₇ octahedra and 1D chains of edge-sharing Cd(2)O₆ octahedra, the Pb²⁺ ions are located at the voids of the structure. The [(B₆O₁₂)⁶⁻] layer exhibits 1D tunnels of 8-membered rings (MRs) which are filled by 1D chains of edge-sharing Cd(2)O₆ octahedra, forming a novel 2D [CdB₆O₁₂]⁴⁻ layer which is also parallel to the ab plane. Neighboring 2D [CdB₆O₁₂]⁴⁻ layers are bridged by dimers of edge-sharing Cd(1)O₇ polyhedra into a novel 3D [Cd₂B₆O₁₂]²⁻ anionic network. EuZnB₅O₁₀ is a new member in the LnMB₅O₁₀ (Ln = rare earth ion and M = divalent metal ion) family, its structure features a 3D network constructed of 2D [B₅O₁₀]⁵⁻ layers that are crosslinked by Zn₂O₁₀ dimers composed of two edge-sharing ZnO₆ octahedra, forming 1D tunnels of Zn₄B₄ 8-membered rings (MRs) along the b-axis which are filled by the Eu³⁺ ions. The luminescent property measurements revealed that EuZnB₅O₁₀ emit strong red light at 610 nm with a ⁵D₀ (Eu³⁺) lifetime of 1.0 ms and a quantum yield of about 18.4%.