posted on 2022-01-10, 15:16authored byYuanyu Yang, Yao Guo, Bingbing Zhang, Ting Wang, Yi-Gang Chen, Xiaohui Hao, Xiaoxiu Yu, Xian-Ming Zhang
The
exploration of nonlinear-/linear-optical crystal materials
with high performance is an extremely difficult research project.
Herein, the two new lead tellurite crystals BaPbTe2O6 and PbVTeO5F were successfully obtained through
a facile hydrothermal synthesis strategy. BaPbTe2O6 lies in the noncentrosymmetric (NCS) and chiral orthorhombic
space group P212121, featuring a unique ∞1[PbTe2O6] chain consisting
of the PbO4 and TeO3 building units, while PbVTeO5F belonging to the centrosymmetric (CS) orthorhombic space
group Pbca manifests a 2D layer made up of ∞1[PbO4F2] chains and novel [V2Te2O10F2] clusters. Further, a systematic analysis
of lead tellurites finds that the coordination geometries of the Pb
atom exert a considerable influence on the connection modes of Pb–O
and Te–O building units. BaPbTe2O6 shows
a great second-harmonic-generation (SHG) effect of ∼5×
the benchmark KH2PO4 (KDP) and a large optical
birefringence of 0.086 at 590 ± 3 nm. PbVTeO5F demonstrates
a remarkably larger birefringence of 0.142 at 590 ± 3 nm, benefiting
from the introduction of the VO5F octahedral unit. Theoretical
studies reveal that the large SHG and birefringence in BaPbTe2O6 can be attributed to TeO3 and PbO4 polyhedra with active lone pairs, while the remarkably enlarged
birefringence in PbVTeO5F is attributable to the highly
distorted octahedral VO5F. The functional orientations
of active building units may offer a practical insight into the design
of the desired optical functional materials.