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Pyrochlores. VI. Preparative chemistry of sodium and silver antimonates and related compounds
Abstract
A number of pyrochlore-structure antimonates MSbyOz (M = Na, Ag, K) have been prepared by dry-firing methods. Each M forms a series of compounds which adopt the pyrochlore structure up to a maximum ratio of M:Sb; the ratio depends on M. Antimony in these compounds is usually present simultaneously in trivalent and pentavalent states.The preparation of the above antimonates by wet methods was also examined. The products obtained were found to depend on the pH of the solution. In acid solution a polyantimonate ion exists which on addition of M salts leads to compounds of formula MSb3Oz, while in alkaline solution the Sb(OH)6− ion exists and MSb(OH)6 antimonates are obtained.A previous literature claim that NaSbO3 occurs with the pyrochlore structure has been disproved. It has been shown that NaSbyOz pyrochlore phases exist only for Na:Sb less than 1:1.5.The preparation of antimonates in the presence of Cl− and from hydrated reactants was carried out. It was concluded that neither Cl− nor OH− or H2O play a significant part in causing an antimonate of Na, Ag, or K to adopt the pyrochlore structure.
... From both the limited available data of the speciation of antimony in water and thermodynamic predictions, the most favoured species of antimony in water is the antimonate ion, also known as the pentavalent oxoanion, SbðOHÞ À 6 (Mohammad et al., 1990; Cotton and Wilkinson, 1999). In addition, an earlier study on the prep-aration of sodium antimonate (Stewart and Knop, 1970) reported that in alkaline solutions, the ionic form of antimony in water is SbðOHÞ À 6 . To this extent, we can infer that under alkaline conditions, water soluble antimony existed as NaSb(OH) 6 , this may explain the enhanced level of antimony in the more alkaline effluents. ...
... In alkaline solutions, antimony is oxidized from its usual Sb(III) oxidation state to a Sb(V) oxidation state (Stewart and Knop, 1970), thus ...
High-impact polystyrene (HIPS) flame retarded with decabromodiphenyl ether (DDE), has been reacted in supercritical water from 380 to 450 degrees C and 21.5 to 31.0 MPa pressure in a batch reactor. Different concentrations of sodium hydroxide additive were used in situ to neutralize the corrosive inorganic bromine species released during the reactions. It appeared that supercritical water conditions lowered the decomposition temperature of both the fire-retardant DDE and HIPS. The reaction products included oils (up to 76 wt%), char (up to 18 wt%) and gas (up to 2.4 wt%) which was mainly methane. The presence of the alkaline water led to up to 97 wt% debromination of the product oil, producing virtually bromine-free oil feedstock. The removal of antimony from the oil product during processing was of the order of 98 wt%. The oil consisted of many single- and multiple-ringed aromatic compounds, many of which had alkyl substituents and/or aliphatic C(n)-bridges (n=1-4). The major single-ringed compounds included toluene, xylenes, ethylbenzene, propylbenzene and alpha-methylstyrene. Bibenzyl (diphenylethane), stilbene, diphenylmethane, diphenylpropane, diphenylcyclopropane, diphenylpropene, diphenylbutane, diphenylbutene and diphenylbuta-1,3-diene were the major C(n)-bridged compounds. Diphenyl ether and acetophenone were the major oxygenated compounds found. The process thus has the potential to produce bromine-free and antimony-free oils from fire-retardant plastics.
... Since no heating process is involved in wall paintings production, it is plausible to assume the addition of pre-synthesized calcium antimonates to the other pigments (mainly yellow and red ochre). This hypothesis is also supported by the fact that the synthesis of antimonates in water solution or humid conditions is not always possible; it requires specific reaction conditions and advanced chemical knowledge [49]. If the mixing of calcium antimonate to pigments is assumed, the purpose of this addition is not yet clear because other white compounds (e.g. ...
During a restoration and diagnostic campaigns carried out on Paestum funerary slabs belonging to the Lucanian funerary art, calcium antimonate (CaSb2O6) was detected for the first time in the pictorial layers. This artificial pigment, widely employed as opacifier both in ancient glass and glaze covering clay objects, was found in the wall paintings, regardless of the colour, supporting the hypothesis of an intentional addition of calcium antimonate to the pigments and the involvement of ceramic painters.
A multi-analytical approach was performed on 32 funerary slabs (6th - 3rd century BCE), currently located at the National Archaeological Museum of Paestum (Italy) using both polarized light microscopy and environmental scanning electron microscopy equipped with energy dispersive X-ray spectrometer, micro X-ray fluorescence, micro Raman spectroscopy, Fourier Transform Infrared spectroscopy and powder X-ray diffraction.
The results confirmed the use of a limited number of pigments, usually applied with fresco technique, although in many cases the stratigraphy of the painted layer showed morphology of mezzo fresco technique, but no organic binders were found. The hues of vegetal decorations were obtained using green earth, sometimes Egyptian blue mixed with yellow ochre, carbon and bone blacks, and orpiment. The alteration of green earth and other iron-containing pigments are likely responsible for the discolouration of the original hues. In red paints, hematite and red ochre are frequently associated with ilmenite, a typical volcanic mineral. Egyptian blue was used in blue paints while in black paints it was mixed with carbon and bone black pigments.
... Powder samples of pyr-Mn 2 Sb 2 O 7 were prepared following the recipe of Brisse [1], with precursor "antimonic acid" first prepared from SbCl 5 (Alfa Aesar, 99.997%) and deionized ice water as described in Ref. [10]. The antimony precursor, once dried, was ground with Mn(Ac) 2 ·4H 2 O (Aldrich, 99.99%) under ethanol. ...
Two polymorphs of Mn2Sb2O7 have been reported, in the pyrochlore structure and in a chiral, monoclinic structure. In both cases, magnetization data have shown prominent features attributable to a ferrimagnetic impurity. Accessing the intrinsic physical properties of both materials thus requires first making them phase pure. We describe our efforts to optimize the preparation of both polymorphs and how we concluded this was necessary, in hopes that future work will be aided by detailed knowledge of this process.
... 9 Nov 2016 rochlore polymorph (Fig. 1a inset) can be stabilized at lower temperatures [13][14][15]. We prepared powder samples of pyr-Mn 2 Sb 2 O 7 following Brisse [13], with precursor 'antimonic acid' prepared from SrCl 5 (Alfa Aesar, 99.997%) and deionized water as in Ref. 25. The precursor was ground with Mn(Ac) 2 ·4H 2 O (Aldrich, 99.99%) then reacted for 12h at a sequence of temperatures from 50 to 550 • C in Al 2 O 3 crucibles in air. ...
In frustrated magnetic systems, geometric constraints or the competition amongst interactions introduce extremely high degeneracy and prevent the system from readily selecting a low-temperature ground state. The most frustrated known spin arrangement is on the pyrochlore lattice, but nearly all magnetic pyrochlores have unquenched orbital angular momentum, constraining the spin directions through spin-orbit coupling. Pyrochlore Mn$_2$Sb$_2$O$_7$ is an extremely rare Heisenberg pyrochlore system, with directionally-unconstrained spins and low chemical disorder. We show that it undergoes a spin-glass transition at 5.5K, which is suppressed by disorder arising from Mn vacancies, indicating this ground state to be a direct consequence of the spins' interactions. The striking similarities to $3d$ transition metal pyrochlores with unquenched angular momentum suggests that the low spin-orbit coupling in the $3d$ block makes Heisenberg pyrochlores far more accessible than previously imagined.
... Synthetic Ag 2 Sb 2 O 6 with a pyrochlore structure is known (Mizoguchi et al., 2004) suggesting that phases that corresponding to one or more Ag-dominant roméite-group species might occur in nature. Natural and synthetic solid solutions with various Ag:Sb ratios that give pyrochlore-like powder X-ray diffraction patterns have been described by Mason and Vitaliano (1953) and Stewart and Knop (1970), respectively. However, the existence of polymorphs of Ag 2 Sb 2 O 6 which do not have the pyrochlore structure (Hong et al., 1974), allows for the possibility that some old descriptions in this category, which were identified on the basis of their composition, may not be members of the pyrochlore supergroup. ...
After careful consideration of the semantics of status categories for mineral species names, minor corrections and disambiguations are presented for a recent report on the nomenclature of the pyrochlore supergroup. The names betafite, elsmoreite, microlite, pyrochlore and roméite are allocated as group names within the pyrochlore supergroup. The status of the names bindheimite, bismutostibiconite, jixianite, monimolite, partzite, stetefeldtite and stibiconite is changed from 'discredited' to 'questionable' pending further research.
... Stoichiometric antimonates of univalent metals with the ideal ( MSb 3+ O 7 , M = Ma, K, Ag) or defect (AgSbO 3 ) pyrochlore structure can be prepared by solid-state reactions [8][9][10][11]. Ryabyshev et al. [11] identified two KSb 3 O 7 -based defect pyrochlore solid solutions with the general formula K m SbO z . One of them ( 0.17 ≤ m < 0.33) can be thought of as K 2 O-deficient KSb 3 defects in these phases and, hence, their transport properties cannot be varied widely. ...
Potassium tungstate antimonates were prepared by calcining K2CO3 + Sb2O3 + 2(1 – – )WO3 mixtures in air. Data on the phase composition of the obtained materials were used to locate the pyrochlore phase region in the Sb2O
z
–W2O6 – K2O composition triangle at 1170 K. The distributions of the constituent ions and lattice defects over the crystallographic positions of space group Fd3m were inferred from structural and gravimetric data. The ac conductivity of the potassium tungstate antimonates was measured from 600 to 1000 K. The conductivity and its activation energy were shown to be correlated with the concentrations of cation (position 16d) and anion (position 8b) defects. The concentration and mobility of K+ ions involved in charge transport were determined.
The structure of the ideal α-pyrochlore with stoichiometry A2M2X6X′ (A—large low-charge cation of alkali, alkaline earth, or rare earth elements), M—a small high-charge cation capable of octahedral coordination (p- or d-elements), X—ions O2– and OH–, F–, or molecules H2O, X′—ions weakly bound to M) has a cubic symmetry with the space group \(Fd\overline{3}m\) (Z = 8). This Chapter is devoted to consideration of the structural features and properties of α-pyrochlore oxides.
From solid state reactions of Ag2O, HgO, and Sb2O3 at high temperatures under elevated oxygen pressures a new silver mercury antimonate, Ag5HgSbO6, has been obtained. According to a single crystal structure determination Ag5HgSbO6 crystallizes in space group P1c (no. 163) with a = 5.9263(4), c = 12.3023(7) Å, V = 374.18(4) Å3, Z = 2, 498 independent reflections, R1 = 0.030, wR2 = 0.059 (I ≥ 2 σ (I). Ag5HgSbO6 consists of HgSbO6 layers, analogous to BiI3, which are separated by Kagome nets formed by Ag+ ions. Perpendicular to these layers and along the c axis linear strings of Ag+ ions run through the large voids of the layers. Accordingly, Ag5HgSbO6 adopts the Ag5Pb2O6 type of structure where the lead positions are occupied by mercury and antimony alternatingly. The finding of mercury in octahedral coordination, particularly besides the lower charged Ag+ cations in linear coordination, which is also highly preferred by Hg2+ ions, is rather unexpected. Ag5HgSbO6 starts to decompose at 450 °C and, in contrast to subvalent and metallic Ag5Pb2O6, the new compound is charge balanced and semiconducting (ρ = 5.7 Ωcm at ambient temperature, Ea = 0.047 eV).
A complete solid solution between the anion-deficient pyrochlore Ag2Sb2O6 and the ideal pyrochlore Cd2Sb2O7 has been synthesized through the standard solid state ceramic method. Each composition has been characterized by various different techniques, including powder X-ray diffraction, optical spectroscopy, electron paramagnetic resonance and 121Sb Mössbauer spectroscopy. Computational methods based on density functional theory complement this investigation. Photocatalytic activity has been studied, and transport properties have been measured on pellets densified by spark plasma sintering. The analysis of the data collected from these various techniques enables a comprehensive characterization of the complete solid solution and revealed an anomalous behavior in the Cd-rich end of the solid solution, which has been proposed to arise from a possible radical O− species in small concentrations.
Secondary antimony minerals play an important role in buffering the dispersion of the element in oxidizing environments, particularly in the supergene zones of Sb-rich ores, mine wastes and other situations where appreciable amounts of Sb are present. The secondary mineralogy of Sb is reviewed and important species highlighted. Attention is drawn to species that require further characterisation. In addition, a summary of reliable solubility data is provided for species for which it is available, pointing towards areas that require further research with respect to the mobility of Sb in the natural environment.
The cubic pyrochlores Cd2Nb2O7, Cd2Ta2O7, Sn2Nb2O7, Sn2Ta2O7. Cd2Sb7O7, Ca2Sb2O7, Mn2Sb2O7, Pb2Sb2O7, and related compounds were prepared and investigated by a number of methods. On heating above 700°. Ca2Sb2O7(pyrochlore) transformed to Ca2Sb2O7(weberite), while Pb2Sb2O7(pyrochlore) changed to a rhombohedrally distorted Pb2Sb2O7 pyrochlore. Refinement of the crystal structures of Cd2Nb2O7 and Cd2Ta2O7 from powder diffractometer intensities yielded 0.434(2) and 0.434(3) respectively as the best estimates of x(O2). Specimens of natural bindheimite and stibiconite were also examined. Stibiconite from San Luis Potosi (Mexico) was shown, on the evidence of its Mössbauer 121Sb spectrum, to contain Sb(V) and Sb(III) in the approximate ratio of 0.2.BaCd2Cl6•5H2O and BaCd2Cl6•2H2O both give powder diffraction patterns of the pyrochlore type. The chlorine could be partially replaced by Br to give mixed crystals BaCd2Cl6−zBrz•5H2O almost up to z = 2.The crystal chemistry of 2–5 oxide pyrochlores and the relationship of the weberite to the pyrochlore phases are discussed.
From solid state reactions of Ag2O and Sb2O3 at high temperatures under elevated oxygen pressures a new silver antimonate, Ag3SbO4, has been obtained. The crystal structure of Ag3SbO4 was determined from powder data (P4122 (no. 91) with a = 7.0436(1), c = 8.8665(1) Å, V = 439.88(2) Å3, Z = 4, Rp = 8,75 %, Rwp = 11.92 %, Rexp = 13.60 % ). Ag3SbO4 is isostructural to Ag3RuO4. The crystal structure is an ordered variant of the NaCl structure and consists of silver atoms and helical chains of edge sharing SbO6 octahedra running along c. Ag3SbO4 is diamagnetic and semiconducting (ρ = 50 Ω·cm at ambient temperature, Ea = 0.098 eV), and starts to decompose at 620 °C.
It is confirmed that AgSbO3 has a pyrochlore related structure without being hydrated. Furthermore, attempts to prepare Ag2Sb2O5(OH)2 or Ag2Sb2O5F2 were unsuccessful. It is concluded that the occurrence of the pyrochlore structure instead of the perovskite structure for certain ABO3 compounds is the result of very strong covalent bonding which tends to restrict oxygen to a maximum coordination number of four.
- P Souchay
P. SOUCHAY and D. PESCHANSKI. Bull. Soc. Chim.
France, 46, 439 (1948).
- A Bellomo
- Ann
B. RICCA, G. D'AMORE, and A. BELLOMO. Ann.
Chirn. Rome, 46, 491 (1956).
- G Von Knorre
- P Olschewsky Ber
G. VON KNORRE and P. OLSCHEWSKY. Ber. Deut.
Chem. Ges. 18, 2353 (1885).
- U Dehlinger
U. DEHLINGER. Z. Kristallogr. 66, 108 (1927).
- W W J Coffeen
- Amer
W. W. COFFEEN. J. Amer. Ceram. Soc. 39, 154
(1956).
- I I M A Aia
- R W Mooney
- C W W Hoffman
I I. M. A. AIA, R. W. MOONEY, and C. W. W. HOFFMAN.
J. Electrochem. Soc. 110, 1048 (1963).
- A Lottermoser
A. LOTTERMOSER. Z. Elektrochem. 33, 514 (1927).
- H E Swanson
- M I Cook
- E H Evans
- J H De Groot
H. E. SWANSON, M. I. COOK, E. H. EVANS, and
J. H. DE GROOT. Nat. Bur. Stand. Circ. 539. Vol.
10, Washington, D.C. 1960. p. 10.
- K H Butler
- M J Bergin
- V M B Hanna-Ford
K. H. BUTLER, M. J. BERGIN, and V. M. B. HANNA-FORD. J. Electrochem. Soc. 97, 117 (1950).
- G Jander
- H Joachim
G. JANDER and H. JOACHIM. Z. Anorg. Allg. Chern.
315, 241 (1962).
- W Brull
G. ~ A N D E R and W. BRULL. Z. Anorg. Allg. Chem.
158, 321 (1926).
- G Jander
- L Brandt
G. JANDER and L. BRANDT. Z. Anorg. Allg. Chem.
147. 5 (1925).
- K Dihlstrom
- A Westgren
K. DIHLSTROM and A. WESTGREN. Z. Anorg. Allg.
Chem. 235, 153 (1937).
- G Natta
- M Baccaredda
- Gazz
G. NATTA and M. BACCAREDDA. Gazz. Chirn. Ital.
66; 308 (1936).
- F Knop
- R E Brisse
- J Meads
- Bainbridge
KNOP, F. BRISSE, R. E. MEADS, and J. BAINBRIDGE.
Can. J. Chem. 46, 3829 (1968).
- F Knop
- L Brisse
- Sutarno Castelliz
- Can
KNOP, F. BRISSE, L. CASTELLIZ, and SUTARNO.
Can. J. Chem. 43, 2812 (1965).
- F Brisse
F. BRISSE and 0. KNOP. Can. J. Chem. 46, 859
(1968).
- F Knop
- L Castelliz Brisse
- Can
0. KNOP, F. BRISSE, and L. CASTELLIZ. Can. J.
Chern. 47, 971 (1969).
- N Schrewelius
N. SCHREWELIUS. Z. Anorg. Allg. Chem. 238, 241
(1 938).
- M H Francombe
M. H. FRANCOMBE and B. LEWIS. Acta Cryst. 11,
175 (1 958).
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