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RESEARCH PRODUCT

X-ray Powder Structure Determination and Thermal Behavior of a New Modification of Pb(II) Selenite

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The crystal structure of a new polymorphic form of lead(II) selenite (PbSeO3) was solved directly from conventional X-ray powder diffraction data. Direct methods and Rietveld refinement techniques were used for the structure determination. The compound crystallizes in the monoclinic space group P21/c (no. 14) with cell dimensions a = 9.1587(1) A, b = 8.0902(1) A, c = 8.7932(1) A, β = 103.032(1)°, and V = 634.76(2) A3. The final refinement gave background excluded Rp = 6.22%, Rwp = 8.81%, and RB = 2.16% by using 45 structural and 15 profile parameters with 10 atoms in an asymmetric unit. The three-dimensional structure consists of 9-coordinated lead atoms, which are linked by three bidentate and three monodentate selenite groups. By combining thermal studies and X-ray powder diffraction, the starting of irreversible phase transition between both polymorphic forms was observed, as now reported structure transformed slowly from space group P21/c to the known structural form P21/m between 315 and 355 °C.