Structure and optical property evolution in PbM(PO4)X (M = Zn, Sn; X = halogen): SHG effect and birefringence

Four new phosphates with a PbM(PO 4 )X formula were synthesized and characterized. Their crystal symmetry, thermal stability and band gap are decreased with an increase of the atomic number of halogen, while the rule for birefringence is the opposite.