PbCd₂B₆O₁₂and 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%.