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4262637 
Journal Article 
Mixed sodium nickel-manganese sulfates: Crystal structure relationships between hydrates and anhydrous salts 
Marinova, DM; Zhecheva, EN; Kukeva, RR; Markov, PV; Nihtianova, DD; Stoyanova, RK 
2017 
Yes 
Journal of Solid State Chemistry
ISSN: 0022-4596
EISSN: 1095-726X 
250 
49-59 
WOS:000400716200006 
The present contribution provides new structural and spectroscopic data on the formation of solid solutions between hydrated and dehydrated sulfate salts of sodium-nickel and sodium-manganese in a whole concentration range: Na2Ni1-x,Mn-x(SO4)(2)center dot yH(2)O, 0 <= x <= 1.0. Using powder XRD, electron paramagnetic resonance spectroscopy (EPR), IR and Raman spectroscopy it has been found that double sodium-nickel and sodium manganese salts form solid solutions Na2Ni1-x,Mn-x(SO4)(2)center dot 4H(2)O with a bliidite-type of structure within a broad concentration range of 0 <= x <= 0.49, while the manganese rich compositions Na2Ni1-x,Mn-x(SO4)(2)center dot 2H(2)O (0.975 <= x <= 1.0) crystallize in the krohnkite-type of structure. The Ni-based bllidites Na2Ni1-x,Mn-x(SO4)(2)center dot 4H(2)O dehydrate between 140 and 260 degrees C into anhydrous salts Na2Ni1-x,Mn-x(SO4)(2), 0 <= x <= 50.44, with a structure where Ni1-x,MnxO6 octahedra are bridged into pairs by edge- and corner sharing SO42- groups. Both TEM and EPR methods show that the Ni2+ and Mn2+ ions are homogenously distributed over three crystallographic positions of the large monoclinic cell. The dehydration of the krohnldte phase Na2Ni1-x,Mn-x(SO4)(2)center dot 2H(2)O yields the alluaudite phase Na2+delta Mn2-delta/2(SO4)(3), where the Na-to-Mn ratio decreases and all Ni2+ dopants are released from the structure. The process of the dehydration is discussed in terms of structural aspects taking into account the distortion degree of the Ni,MnO6 and SO4 polyhedra. 
Double sodium transition metal sulfates; Sulfate-based minerals; Electrode materials for sodium ion batteries,crystal structure; Spectroscopic analysis (IR and Raman spectroscopy EPR)