Synthesis, crystal growth, properties of a new neodymium-niobium-tellurite NdNbTe2O8 and comparison with compounds of same structural type

A new neodymium-niobium-tellurite compound, NdNbTe 2 O 8 , was successfully obtained through high-temperature solution method. NdNbTe 2 O 8 crystallized in the centrosymmetric space group P 2 1 / c with unit cell parameters of a  = 5.6146(6) Å, b  = 21.936(2)   Å, c  = 8.0905(6) Å, β = 136.09°, and Z = 4. Its structure is composed of two alternately arranged layers consisting of NbO 6 octahedra and NdO 8 polyhedra, with TeO 3 trigonal pyramids linked the layers to form a 3-dimensional framework. This particular structural feature has been discovered in a series of recent found new compounds with similar compositions of RMQ 2 O 8 (R = Y, La, Nd; M = V, Nb; Q=Se, Te) including the noncentrosymmetric LaNbTe 2 O 8 with favorable nonlinear optical properties. The structural evolution, crystal growth, thermal analysis and optical spectrum of the title compound are also presented.