Evolution of crystal structure of PbMoO4 between 5 and 300 K: A low temperature powder neutron diffraction study

Abstract

Evolution of crystal structure of PbMoO4 (Wulfenite, tetragonal, I41/a) from 5 to 300 K by in situ low temperature powder neutron diffraction studies is reported. The study revealed no structural transition in the complete range of temperature. The unit cell parameters show anisotropic expansion with about 2.2 times higher expansion along c-axis compared to that along a-axis. From the refined structural parameters, it is emphasized that the expansion of Pb–O bonds in PbO8 (bisdisphenoid) units and their orientations along a- and c-axes are the controlling factors. The MoO4 tetrahedra behaves like a rigid unit in the temperature range of this study. The expansion of unit cell volume is fully arising from the expansion of PbO8 bisdisphenoids. The analyses of anisotropic displacement parameters also show almost smooth variation with temperature down to 5 K. The evolutions of structural parameters of PbMoO4 with temperature suggest it for a promising material for cryogenic applications.