Synthesis, crystal structure, spectroscopic and optical properties of the new phosphate Pb0.954(3)Mn2(PO4)2.

The polycrystalline orthophosphate Pb 0.954(3) Mn 2 (PO 4) 2 was obtained at 830 ​°C in a melt with NaCl. This compound is isostructural to SrMn 2 (PO 4) 2 (structural type Mg 3 (PO 4) 2): its triclinic system, a ​= ​8.86706(7) Å, b ​= ​9.00697(8) Å, c ​= ​10.35293(10) Å, α ​= ​123.9418(5)°, β ​= ​91.1907(5)°, γ ​= ​89.8282(7)°, space group P 1 ¯ , Z ​= ​4 (R w p = ​1.47%, Rp ​= ​1.13%, χ2 ​= ​2.234, R(F2) ​= ​3.73%) can be described as a hexagonal close packing of phosphate groups. Octahedral, tetrahedral, and trigonal-bipyramidal voids within the [PO 4 ]-packing provide positions for 8-fold and 10-fold [PbO x ] and distorted octahedron [MnO 6 ]. To maintain the valence balance, lead deficiency must be compensated for by a change in the oxidation state of a part of manganese: Pb 0.954(3) Mn+2 1.908 Mn+3 0.092 (PO 4) 2. The IR and Raman spectroscopy of the sample were studied. The energy of the optical band gap E g determined by the Tauc plot method is 4.2 ​eV. Crystallization of lead barium phosphate in NaCl melt. [Display omitted] • A new double orthophosphate Pb 0.954(3) Mn 2 (PO 4) 2 was synthesized in NaCl melt. • The crystal structure, IR, RS of the double orthophosphate were studied. • The band gap of the new compound is 4.2 ​eV. [ABSTRACT FROM AUTHOR]