A new structural phase of MgV2O6 was obtained by a high-pressure,high-temperature(HPHT) synthesis method.The new phase was investigated by the Rietveld analysis of X-ray powder diffraction data,showing space group Pbcn(No.60) symmetry and a = 13.6113(6) (1 = 0.1 nm),b = 5.5809(1) ,c = 4.8566(3) ,V = 368.93(2) 3(Z = 4).High pressure behavior was studied by Raman spectroscopy at room temperature.Under 22.5 GPa,there was no sign of a structural phase transition in the spectra,demonstrating stability of the HPHT phase up to the highest pressure.
Double perovskite oxide Sr2Co Fe O6(SCFO)has been obtained using a high-pressure and high-temperature(HPHT)synthesis method.Valence states of Fe and Co and their distributions in SCFO were examined with X-ray photoelectron spectroscopy.The electric transport behavior of SCFO showed a semiconductor behavior that can be well described by Mott’s law for variable-range hopping conduction.The structural stability of SCFO was investigated at pressures up to 31GPa with no pressure-induced phase transition found.Bulk modulus B0was determined to be 163(2)GPa by fitting the pressure–volume data to the Birch–Murnaghan equation of state.
The structural and magnetic properties of SmFeO3with B site substitution of non-magnetic atom Al are investigated.The x-ray diffraction patterns show that SmFe(1-x)AlxO3 remains an orthorhombic structure within the whole doping range, and the unit-cell volume decreases monotonically with the increase of doped Al concentration. Besides, the octahedral tilting distortions of FeO6are found to be alleviated while the tolerance factor increases. However, the relationship between the lattice parameters and Al concentration is observed to deviate from Vegard's rule, and this may be caused by magnetostriction effects. For the doping content values in a range 0 ≤ x ≤ 0.6, the ferromagnetism, antiferromagnetism,and paramagnetism are observed to occur continuously. Moreover, the magnetization and the spin reorientation temperature(Tk) decrease monotonically as Al content value increases. With the doping content values being x = 0.8 and 1.0, these compounds only show paramagnetic behavior.
The high-pressure behaviors of SmFeO3are investigated by angle-dispersive synchrotron X-ray powder diffraction under a pressure of up to 40.3 GPa at room temperature. The crystal structure of SmFeO3remains stable at up to the highest pressure. The different pressure coefficients of the normalized axial compressibility are obtained to be βa = 0.60 ×10-3GPa-1, βb= 0.79 × 10-3GPa-1, βc = 1.28×10-3GPa-1, and the bulk modulus(B0) is determined to be 293(3) GPa by fitting the pressure–volume data using the Birch–Murnaghan equation of state. Furthermore, the larger compressibility of the FeO6octahedra suggests the evolution of the orthorhombic structure towards higher symmetry configuration at high pressures.
