Аннотация
AHfO(3) (A = Ca, Sr and Ba) belongs to perovskite family with general
formula A(2+)B(4+)O(3). The crystal structure of CaHfO(3) (CH), SrHfO(3)
(SH) and BaHfO(3) (BH) at room temperature (RT) is reported, combining
the results of the Rietveld method refinements using X-ray and neutron
powder diffraction data and PAC spectroscopy. The structures were
refined by the Rietveld Method using DBWS9411 and GSAS programs, The
refinement of SH using neutron and X-ray powder pattern indicates an
orthorhombic Pnma symmetry at room temperature. The hyperfine parameters
of PAC spectroscopy indicate that the structure has lower-than-cubic
symmetry at RT, The structures of CH and BH were refined with the Pnma
and Pm (3) over bar m space group respectively. The three compounds have
near regular oxygen octahedra that are characteristic of perovskites of
Glazer types a(+)a(-)a(-) and a(0)a(0)a(0), for which the distortion is
better related to the tilting of the octahedra.
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