Materials Chemistry and Physics, Vol.163, 286-292, 2015
New bismuth borophosphate Bi4BPO10: Synthesis, crystal structure, optical and band structure analysis
New bismuth borophosphate Bi4BPO10 was obtained by spontaneous crystallization from the melt of correspondent composition at 804 degrees C. Crystal structure with orthorhombic lattice parameters: a = 22.5731(3) angstrom, b = 14.0523(2) angstrom, c = 5.5149(1) angstrom, V = 1749.34(4), Z = 8, SG Pcab was determined by X-ray powder diffraction technique. The [Bi2O2](2+) -layers, which are typical for bismuth oxide compounds, transform into cationic endless strips of 4 bismuth atoms width directed along the c-axis in Bi4BPO10. The strips combining stacks are separated by flat triangle [BO3](3-) -anions within stacks. Neighboring stacks are separated by tetrahedral [PO4](3-)-anions and shifted relatively to each other. Bismuth atoms are placed in 5-7 vertex oxygen irregular polyhedra. Bi4BPO10 is stable up to 812 degrees C, then melts according to the peritectic law. The absorption spectrum in the range 350-700 nm was obtained and the width of the forbidden band was estimated as 3.46 eV. The band electronic structure of Bi4BPO10 was modeled using DFT approach. The calculated band gap (3.56 eV) is in good agreement with the experimentally obtained data. (C) 2015 Elsevier B.V. All rights reserved.