Synthesis, X-ray diffraction investigations and spectroscopic analysis of yttrium-substituted pyrochlore oxides Y2−2xBi2xTi2O7 via a sol–gel process

Synthesis, X-ray Rietveld analysis, infrared and Mössbauer spectroscopy of R 2 FeSbO 7 (R 3+ = Y, Dy, Gd, Bi) pyrochlore solid solution

“…6 shows the FT-IR spectra operating in the transmission mode recorded on the polycrystalline powder of Y 2 FeSbO 7 over a wavenumber range of 400−1000 cm −1 in the mid-infrared region. Though seven characteristics IR transmission bands, to be consistent with the theoretical analysis, are usually observed in the range of 100−1000 cm −1 for other pyrochlore compounds [1,9,25], due to our experimental limitation we could not record IR spectra precisely below 420 cm −1 . Only three or four IR active bands are found for the pyrochlores within the phonon wavenumbers range of 400−750 cm −1 [1,[26][27][28][29][30][31], as also recorded in the present study.…”

“…A salient feature of the observed IR spectra of Y 2 FeSbO 7 compound is that there is a very strong and broad band F 1u (1) at high wavenumber end at 642.0 cm −1 followed by some low intensity bands at 490, 465, 447 and 432 cm −1 . The band at 642 cm −1 can be ascribed to the stretching vibration of smallest interatomic bond M(Fe/Sb)−O in MO 6 octahedron [1,9,25]. Literature review showed that high wavenumber IR band was normally found in a wide region of 700 −500 cm −1 for the pyrochlore compounds [1].…”

Raman scattering and X‐ray diffraction on YBiTi2O7 prepared at low temperature

“…If the correlation between the cell parameters and the E g mode wavenumber shows no particular dispersion from the mean line, a higher deviation on the correlation between bismuth molar ratio and wavenumber is observed with the points corresponding to the solid-state route and the less rich in the bismuth phase in the mixture of pyrochlores, prepared in Ref. 8 For the Raman spectra obtained from the sample prepared in our first study by the sol-gel process without additional ligands, after annealing at 1000°C, 8 depending on the area of analysis, two different spectra (f and g curves in Fig. 1) were observed in good agreement with the XRD characterisation, which revealed a mixture of two pyrochlores.…”

“…These events were presumed to result from the removal of free volatile species, not strongly chelated to any of the metal cations in the gel network (most of which are already removed by the drying process). 8 The endothermic peak at 85°C on the DTA curve was assigned to the elimination of residual water. Another endothermic peak was to be noticed at 270°C on the DTA curve, which indicates the melting of the gel.…”

“…In a first study, we confirmed the possibility of preparation of bismuth-doped Y 2 Ti 2 O 7 but a pure phase was not obtained. 8 In the present study, the conditions of preparation were optimised by the addition of chelating ligands in the sol-gel process. The composition YBiTi 2 O 7 was also prepared by a solid-state route for comparison.…”