Synthesis, structure, and high temperature Mössbauer and Raman spectroscopy studies of Ba1.6Sr1.4Fe2WO9 double perovskite

X-ray structure refinement of solid solution Ba2.15−xNa0.7+xNb5−xWxO15 and the investigation of the orthorhombic-tetragonal phase transition by Raman spectroscopy

“…This is similar to the 248 and 628 cm À1 modes observed in LiNbO 3 and to the 260-280 cm À1 and 630-650 cm À1 modes reported for Pb 2(1Àx) K 1+x Gd x Nb 5 O 15 [40]. Finally, in analogy with perovskites [41], the highest-frequency mode around 850-938 cm À1 might be connected with a stretching vibration of (Nb/W)O 6 octahedra.…”

Synthesis and Rietveld refinements of new ceramics Sr2CaFe2WO9 and Sr2PbFe2TeO9 perovskites

“…In fact, the average (Fe/M )-O bond lengths obtained from Rietveld refinements of the compounds Sr 2 CaFe 2 WO 9 and Sr 2 PbFe 2 TeO 9 are very similar to those found in other oxides with Fe 3+ and W 6+ or Te 6+ cations (Ivanov et al, 2001;Viola et al, 2005;Manoun et al, 2011) and in agreement with the individual Fe 3+ , W 6+ , Te 6+ -O bond length calculated from Shannon's ionic radii (Fe-O = 2.065 Ǻ, W-O = 2.02 Ǻand Te-O = 1.96 Å) for high-spin electron configuration in octahedral coordination (Shannon, 1976).…”

“…These antisite defects play an important role in ions surface interaction process and influence the electrical and optical behaviors. The antisite-disorder was also observed in several triple perovskites, such as Sr 3 Fe 2 TeO 9 (S space group I 4/ m ), Ba 3 Fe 2 TeO 9 (space group P 6 3 / mmc ) (Ivanov et al , 2007; Tang et al , 2016), Ca 3 Fe 2 WO 9 (space group I 4/ m ) (Ivanov et al , 2005), Sr 3 Fe 2 MoO 9 (space group I 4/ m ), Sr 3 Fe 2 WO 9 (space group I 4/ m ), Sr 3 Fe 2 UO 9 (space group I 4/ m ) (Viola et al , 2003), Ba 1.6 Sr 1.4 Fe 2 WO 9 (space group P 6 3 / mmc ) (Manoun et al , 2011). Recently perovskite series Sr 3−x Ca x Fe 2 TeO 9 (0 ⩽ x ⩽ 1) (El Hachmi et al , 2017) were reported by our research team showing that the antisite-disorder is affected with increasing the Calcium amount from x = 0 to x = 1.…”

X-ray diffraction and Raman spectroscopy studies of temperature and composition induced phase transitions in Ba2−xSrxZnWO6 (0≤x≤2) double perovskite oxides

“…Li et al [12] studied the effect of the composition on the electrical properties of BaBi 1−x Sb x O 3 (0 ≤ x ≤ 0.5) negative temperature coefficient (NTC) thermistors. Manoun et al [13] reported synthesis, structure, and high temperature Mössbauer and Raman spectroscopy studies of Ba 1.6 Sr 1.4 Fe 2 WO 9 double perovskite, the results allow concluding that a temperature-induced phase transition had occurred. The high temperature Raman and Mössbauer results showed the magnetic to paramagnetic transition.…”