TITLE

On the formation of solid solutions with blödite- and kröhnkite-type structures

AUTHOR(S)
Marinova, D.; Stoyanova, R.; Stoilova, D.; Georgiev, M.; Bancheva, Tsv.
PUB. DATE
December 2017
SOURCE
Journal of Thermal Analysis & Calorimetry;Dec2017, Vol. 130 Issue 3, p1925
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
In this contribution, we provide experimental results on the synthesis and some properties (structural, spectroscopic and thermal) of limited solid solutions NaNiCu(SO)·4HO (0 < x ≤ 0.17). Based on different experimental methods-vibrational spectroscopy (infrared and Raman), X-ray powder diffraction at ambient and elevated temperature, electron paramagnetic resonance spectroscopy (EPR) and TG-DTA-DSC methods, it has been established that the copper ions are included in the nickel blödite-type structure up to about 17 mol%. However, the nickel ions are not able to accept the coordination environment of the copper ions in the strongly distorted [Cu(HO)O] clusters due to the Jahn-Teller effect, thus resulting in the crystallization of a kröhnkite free from nickel ions. The X-ray powder diffraction data show that the included copper ions do not influence considerably on the lattice parameters of the blödite matrix owing probably to the buffer effect of the sodium ions and hydrogen bonds. The vibrational spectra are interpreted in the light of their crystal structures. The TG and DTA methods combined with X-ray powder diffraction at elevated temperature reveal that the dehydration of NaNi(SO)·4HO and NaNiCu(SO)·4HO solid solutions occurs stepwise, thus forming dihydrates and anhydrous compounds-NaNi(SO) and NaNiCu(SO) of the same structures. It has been found that the increased amount of copper ions causes increasing in the values of Δ H and decreasing in the values of Δ H of the solid solutions. EPR spectra of the solid solutions are presented and compared to that of NaZnCu(SO)·4HO.
ACCESSION #
126260549

 

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