Preparation and characterization of metastable trigonal layered MSb₂O₆ phases (M = Co, Ni, Cu, Zn, and Mg) and considerations on FeSb₂O₆

Abstract

MSbO compounds (M = Mg, Co, Ni, Cu, Zn) are known in the tetragonal trirutile forms, slightly distorted monoclinically with M = Cu due to the Jahn-Teller effect. In this study, using a low-temperature exchange reaction between ilmenite-type NaSbO and molten MSO-KCl (or MgCl-KCl) mixtures, these five compositions were prepared for the first time as trigonal layered rosiaite (PbSbO)-type phases. Upon heating, they irreversibly transform to the known phases via amorphous intermediates, in contrast to previously studied isostructural MnSbO, where the stable phase is structurally related to the metastable phase. The same method was found to be applicable for preparing stable rosiaite-type CdSbO. The formula volumes of the new phases show an excellent correlation with the ionic radii (except for M = Cu, for which a Jahn-Teller distortion is suspected) and are 2-3% larger than those for the known forms although all coordination numbers are the same. The crystal structure of CoSbO was refined via the Rietveld method: P3[combining macron]1m, a = 5.1318(3) Å, and c = 4.5520(3) Å. Compounds with M = Co and Ni antiferromagnetically order at 11 and 15 K, respectively, whereas the copper compound does not show long-range magnetic order down to 1.5 K. A comparison between the magnetic behavior of the metastable and stable polymorphs was carried out. FeSbO could not be prepared because of the 2Fe + Sb = 2Fe + Sb redox reaction. This electron transfer produces an additional 5s shell for Sb and results in a volume increase. A comparison of the formula volume for the stable mixture FeSbO + 0.5SbO with that extrapolated for FeSbO predicted that the trirutile-type FeSbO can be stabilized at high pressures.

Chirality and Magnetocaloricity in GdFeTeO6 as Compared to GdGaTeO6

“…Correlation between crystal radii [6] of RE 3+ and hexagonal subcell parameters of REFeTeO6. Red diamonds, a; blue triangles, c/2; RE = La [1,3,4], Pr, Nd, Sm [4], and Gd (this work); green circles, same from Reference [5]., Figure S3. (a) Effect of changing UGd (eV) for the energy differences of one AFM and 3 FiM states with respect to the FM state.…”

“…Comparison of the two XRD patterns of nominal "GdFeTeO6" taken in CuKα radia-tion. Upper panel: Relatively pure phase prepared from oxides for 48 h at 700 °C [5]. Lower pan-el: mixed phase prepared by the semi-wet method for 56 h at 750 °С with three intermediate re-grindings (this work)., Figure S2.…”

“…It is organized by diluted triangular A and dense honeycomb B layers alternating along the trigonal axis c [3]. In case of the A position being occupied by the divalent transition metal ions (M = Mn, Co, Ni), the long-range antiferromagnetic (AFM) order takes place at low temperatures in both MAs 2 O 6 arsenates [4] and MSb 2 O 6 antimonates [5]. Exceptionally, CuSb 2 O 6 [5] does not order down to 1.5 K, while PdAs 2 O 6 orders at an unusually high Néel temperature 140 K [6].…”

“…In case of the A position being occupied by the divalent transition metal ions (M = Mn, Co, Ni), the long-range antiferromagnetic (AFM) order takes place at low temperatures in both MAs 2 O 6 arsenates [4] and MSb 2 O 6 antimonates [5]. Exceptionally, CuSb 2 O 6 [5] does not order down to 1.5 K, while PdAs 2 O 6 orders at an unusually high Néel temperature 140 K [6]. The couple of pentavalent cations in the B layer can be substituted by a combination of tetravalent and hexavalent cations, as is the case of MnSnTeO 6 [7].…”

MnSnTeO6: A Chiral Antiferromagnet Prepared by a Two-Step Topotactic Transformation

“…In the MSb 2 O 6 series, all M 2+ cations larger than Mn 2+ (M = Cd, Ca, Sr, Pb, and Ba) give rise to the rosiaite structure type whereas all stable compounds with M 2+ cations smaller than Mn 2+ (M = Mg, Co, Ni, Cu, and Zn) belong to the trirutile structure type, 21,22 although metastable rosiaite-type polymorphs were also prepared. 22 All known M 2+ As 2 O 6 (M =Ni, Co,Mn, Pd, Ca, Pb) are also rosiaites. [23][24][25][26] Both trirutile and rosiaite types are centrosymmetric and, thus, less interesting than MnSb 2 O 6 .…”