High-Pressure Synthesis, Crystal Structure, and Semimetallic Properties of HgPbO3

The crystal structure of HgPbO3 was studied using single-crystal X-ray diffraction and powder synchrotron X-ray diffraction. The structure was well characterized as a centrosymmetric model with a space group of R-3m [hexagonal setting: a = 5.74413(6) A and c = 7.25464(8) A] rather than as a noncentrosymmetric model as was expected. It was found that Pb4+ is octahedrally coordinated by six oxygen atoms as usual, while Hg2+ is coordinated by three oxygen atoms in a planar manner, this being a very rare coordination of Hg in a solid-state material. The magnetic and electronic transport properties were investigated in terms of the magnetic susceptibility, magnetization, Hall coefficient, and specific heat capacity of polycrystalline HgPbO3. Although HgPbO3 has a carrier concentration (=7.3–8.5 × 1020 cm–3) that is equal to that of metallic oxides, the very weak temperature dependence of the electrical resistivity (residual-resistivity ratio ∼1.5), the significant diamagnetism (= –1.02 × 10–4 emu mol–1 at 300 ...