“…The bands at 870 and 820 cm -1 are due to vibration of the WO 2 entity present in the W 2 O 8 groups. The bands at 685 and 620 cm -1 are typical of a two-oxygen bridge (W 2 O 2 ) and are due to the asymmetric stretching of the same units. ,− The vibrations of the NiO 6 polyhedra are in the absorption range below 500 cm -1 3 IR spectra of the sample prepared by mechochemical synthesis: (a) nonactivated sample; (b) mechanical activation for 2.5 h; (c) mechanical activation for 5 h; (d) mechanical activation for 7.5 h; (e) mechanical activation for 10 h. 4 X-ray photoelectron spectra of the Ni2p level: (a) mechanical activation sample for 2.5 h; (b) mechanical activation sample for 5 h; (c) mechanical activation sample for 10 h. …”
Section: Resultsmentioning
confidence: 99%
“…20 The observed absorption bands are in good agreement with IR data on other crystalline phases belonging to the wolframite structure. 10,21,22 The vibrational spectra of compounds containing Me 2 O 8 (Me ) Mo or W) structural units have been analyzed using Factor group analysis and the correlation method. [21][22][23] Taking into account structural data and vibrational spectra of these compounds, we attributed the vibrational bands of the NiWO 4 .…”
Section: Resultsmentioning
confidence: 99%
“…The bands at 685 and 620 cm -1 are typical of a two-oxygen bridge (W 2 O 2 ) and are due to the asymmetric stretching of the same units. 10,[21][22][23] The vibrations of the NiO 6 polyhedra are in the absorption range below 500 cm -1 . 19 XPS Analysis.…”
The possibilities of mechanochemical activation as a successful route for direct synthesis of NiWO4 have
been studied. A stoichiometric mixture of NiO and WO3 in a 1:1 molar ratio was subjected to intense mechanical
treatment in air using a planetary ball mill for different periods of time. The phase and structural transformations
were monitored by X-ray diffraction (XRD), infrared spectroscopy (IR), and X-ray photoelectron spectroscopy
(XPS). It was found that 7.5 h of milling of the reagents leads to complete crystallization of single
nanostructured phase NiWO4 at room temperature.
“…The bands at 870 and 820 cm -1 are due to vibration of the WO 2 entity present in the W 2 O 8 groups. The bands at 685 and 620 cm -1 are typical of a two-oxygen bridge (W 2 O 2 ) and are due to the asymmetric stretching of the same units. ,− The vibrations of the NiO 6 polyhedra are in the absorption range below 500 cm -1 3 IR spectra of the sample prepared by mechochemical synthesis: (a) nonactivated sample; (b) mechanical activation for 2.5 h; (c) mechanical activation for 5 h; (d) mechanical activation for 7.5 h; (e) mechanical activation for 10 h. 4 X-ray photoelectron spectra of the Ni2p level: (a) mechanical activation sample for 2.5 h; (b) mechanical activation sample for 5 h; (c) mechanical activation sample for 10 h. …”
Section: Resultsmentioning
confidence: 99%
“…20 The observed absorption bands are in good agreement with IR data on other crystalline phases belonging to the wolframite structure. 10,21,22 The vibrational spectra of compounds containing Me 2 O 8 (Me ) Mo or W) structural units have been analyzed using Factor group analysis and the correlation method. [21][22][23] Taking into account structural data and vibrational spectra of these compounds, we attributed the vibrational bands of the NiWO 4 .…”
Section: Resultsmentioning
confidence: 99%
“…The bands at 685 and 620 cm -1 are typical of a two-oxygen bridge (W 2 O 2 ) and are due to the asymmetric stretching of the same units. 10,[21][22][23] The vibrations of the NiO 6 polyhedra are in the absorption range below 500 cm -1 . 19 XPS Analysis.…”
The possibilities of mechanochemical activation as a successful route for direct synthesis of NiWO4 have
been studied. A stoichiometric mixture of NiO and WO3 in a 1:1 molar ratio was subjected to intense mechanical
treatment in air using a planetary ball mill for different periods of time. The phase and structural transformations
were monitored by X-ray diffraction (XRD), infrared spectroscopy (IR), and X-ray photoelectron spectroscopy
(XPS). It was found that 7.5 h of milling of the reagents leads to complete crystallization of single
nanostructured phase NiWO4 at room temperature.
“…Chapter 10 -Trigonal double molybdates and tungstates Inconsistent data as to a phase transition temperature in KIn(WO4)2 are reported in literature. In the early 80's, from microscopic studies it has been shown [34] that the structural transition from a trigonal to monoclinic system in KIn(WO4)2, resulting in a ferroelastic ordering, occurs at T1=454 K. Much later, based on infrared and Raman spectroscopy [70] a higher transition temperature was obtained. Its value (475 ±16 K) was found from the fitting the data of the split Raman-active band as the function of temperature.…”
Section: Introductionmentioning
confidence: 99%
“…The ferroelastic transitions in TDM/T have been evidenced by anomalies in the Raman [30,47,67,70,[73][74][75][76][77][78][79] and Brillouin spectra [74,75,80,81] , ultrasonic studies [82] , x-ray measurements [83][84][85] , heat capacity [86] as well as in electron paramagnetic resonance (EPR) spectra [48,50,51,53,[56][57][58][59][60]83,[87][88][89][90][91][92][93][94][95][96][97] . Re-building of the ferroelastic domain structure in compounds exhibiting a sequence of phase transitions has been observed using a polarized-ligth microscopy [60,95,96,[98][99][100][101][102][103] .…”
The overview contains basic information about trigonal double molybdates and tungstates MR(XO4)2, representing a crystal family with layered structure. Their structure features networks of corner-linked RO6 octahedra and XO4 Â tetrahedra. Many compounds of this crystal family exhibit ferroelastic phase transitions. Their ferroelastic properties are discussed, with particular emphasis on the peculiarities of the domain structure. An overview of results of studies on ferroelastic phase transitions, obtained with various experimental methods, is provided. Models of trigonal unit cell distortion are presented for monoclinic phases of KSc(MoO4)2 and RbIn(MoO4)2 crystals.
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