Structure and vibrational dynamics of sodium sulfate/sodium chromate solid solutions

Abstract

Structural relaxation on quenched lithium sulphate AIP Conf.Solid solutions of Na 2 SO 4 /Na 2 CrO 4 are studied using laser Raman spectroscopy, infrared spectroscopy and differential scanning calorimetry. When the chromate ion concentration increases, the lattice expands continuously and a higher temperature sulfate phase, phase III, is stabilized to room temperature. The site group and correlation field splitting are also studied as a function of the relative sulfate‫گ‬chromate ion concentration. The transition enthalpy from phase III to a higher temperature sulfate phase, phase I, has been measured. The calculated transition entropy is perfectly explained by a mixing entropy model.

Raman study of different crystalline forms of PbCrO4 and PbCr1−xSxO4 solid solutions for the noninvasive identification of chrome yellows in paintings: a focus on works by Vincent van Gogh

“…Consistent with the XRD data (Table and Fig. S1 of Supporting Information) and with previous studies on other MCr 1−x S x O 4 compounds ( M = Ba, Ca, Sr, Pb, and Na), these observations can be explained taking into account the lattice compression effect. Also, the changes in the band‐shape, more symmetrical at low sulfate content, must be considered in this sense.…”

“…Consistent with the XRD data (Table 1 and Fig. S1 of Supporting Information) and with previous studies on other MCr 1Àx S x O 4 compounds (M = Ba, Ca, Sr, Pb, and Na), [39][40][41] these observations can be explained taking into account the lattice [23] for the spectra acquired by means of the portable device at 785 nm. compression effect.…”

Degradation Process of Lead Chromate in Paintings by Vincent van Gogh Studied by Means of Spectromicroscopic Methods. 3. Synthesis, Characterization, and Detection of Different Crystal Forms of the Chrome Yellow Pigment

“…In the ν 3 chromate asymmetric stretching region (930–800 cm –1 ), both a band broadening and a shift toward higher wavenumbers is detected when the amount of chromate decreases. Consistent with the XRD data (Table ) and studies on other MCr 1‑ x S x O 4 ( M = Ba, Ca, Sr, Pb, and Na), − this is justified by changes in the crystalline structure.…”

“…The full width at half-maximum (fwhm) of this component also increases. These observations can be explained by the lattice compression effect and the prevention of intermolecular coupling occurring when sulfate replaces the chromate anions inside the structure. , …”

“…These observations can be explained by the lattice compression effect and the prevention of intermolecular coupling occurring when sulfate replaces the chromate anions inside the structure. 24,25 With increasing amount of sulfate, a progressive shift of the position toward highest energy, increase of the FWHM, and a change of the relative intensities are also seen for the components describing the chromate bending modes (400−280 cm −1 ) (Figure S-3B of the Supporting Information). Consistent with the literature, 28,29 for S 1mono , the ν 4 (CrO 4 2−…”