A terbium rich orthoborate LiSrTb2(BO3)3 and its analogues

Abstract

A terbium rich orthoborate, LiSrTb₂(BO₃)₃, has been successfully synthesized by a solid state reaction and crystallized from a high temperature flux. Single crystal X-ray diffraction results show that LiSrTb₂(BO₃)₃ possesses the Pm1 space group, with cell parameters of a = 10.3845(4) Å, c = 6.4739(8) Å, and Z = 3. In the structure, the terbium atom coordinates to eight oxygen atoms to yield a TbO₈ polyhedron. These polyhedra are connected with each other to form a layer of trigonal [Tb₃O₂₁] and hexagonal [Tb₆O₃₃] blocks in the ab plane, and then the layers are further linked by the triangular BO₃ groups along the c direction. The magnetic susceptibility measurements show that LiSrTb₂(BO₃)₃ exhibits paramagnetic behaviors from 2 K to 300 K. The diffuse optical reflection spectrum indicates that LiSrTb₂(BO₃)₃ is transparent in the range 500–1500 nm, and effective green emission is detected in the photoluminescence of LiSrTb₂(BO₃)₃. In addition, a series of isostructural lanthanide analogues LiSrLn₂(BO₃)₃ (Ln = Pr, Nd, Sm–Lu) and LiBaLn₂(BO₃)₃ (Ln = Pr, Nd, Sm–Tm) have also been prepared by solid state reactions.