FIGURE 3 - uploaded by Luca Bindi
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BO 6 octahedra forming a HTB motif in the M layer of ingersonite (a) and pyrochlore (b) with the underlying N layer showing the difference in the relative position of the isolated BO 6 octahedron belonging to the N layer. Circles represent the A cations; in particular, smaller gray circles represent Mn 2+ and larger white circles represent Ca.
Source publication
The crystal structure of ingersonite, [Ca2.93Mn1.062+Fe0.012+][Sb3.955+Mg0.05]F0.15O13.85, refined in the space group P3(1)21 [a = 7.282(2), c = 17.604(4) angstrom, V= 808.4(3) angstrom(3), Z = 3] to R = 2.32% for 2219 F-0 > 4 sigma(F-0) using MoK alpha X-ray data. The structure of ingersonite is isostructural with the synthetic weberite-3T polytyp...
Contexts in source publication
Context 1
... Therefore, the stacking of successive pairs of M and N layers in ingersonite is the same as in pyrochlore. Nonetheless, there is a difference in the relative position between M and N layers in ingersonite and pyrochlore. As an M layer is projected down the trigonal axis together with the underlying N layer, it appears that in ingersonite (Fig. 3a) the B1 octahedron is shifted ½ [010] (at z ~ 0) with respect to the ideal position in pyrochlore, where the B octahedron belonging to the N layer lies just below the triangular ring of the M layer (Fig. 3b). In the successive MN pairs, the shift of the N layer with respect to the same layer in pyrochlore is ½[1 10] (at z ~ 1/3) and ...
Context 2
... and pyrochlore. As an M layer is projected down the trigonal axis together with the underlying N layer, it appears that in ingersonite (Fig. 3a) the B1 octahedron is shifted ½ [010] (at z ~ 0) with respect to the ideal position in pyrochlore, where the B octahedron belonging to the N layer lies just below the triangular ring of the M layer (Fig. 3b). In the successive MN pairs, the shift of the N layer with respect to the same layer in pyrochlore is ½[1 10] (at z ~ 1/3) and ½[100] (at z ~ 2/3). As a consequence of the difference in the relative position between M and N layers, the anions play a different crystal- chemical role in ingersonite with respect to pyrochlore. In the ...
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Citations
... In terms of an anion-centered polyhedral description, the zirconolite polytypes preserve the anion ordering on 7/8 of the tetrahedral interstices as observed in pyrochlore (Zanazzi et al., 2009). Both weberite-and zirconolite-type A 2 B 2 X 7 compounds can be described as a sequence of A 3 B-and B 3 A-pyrochlore-type layers (Bonazzi and Bindi, 2007). A and B cations form a distorted face-centered cubic array. ...
... Ingersonite (Dunn et al., 1988), Ca 3 Mn 2+ Sb 5+ 4 O 14 , is trigonal, space group P3 1 2. The type occurrence is Långban mine, Långban Ore District, Filipstad, V€ armland County, Sweden. It is isostructural with the synthetic weberite-3T polytype (Bonazzi and Bindi, 2007) and could be considered a 3T polytype of oxycalciorom eite ( Fig. 1.8). ...
... Ingersonite crystal structure(Bonazzi and Bindi, 2007) drawn using VESTA 3(Momma and Izumi, 2011). ...
Many synthetic compounds with a crystal structure derived from that of fluorite have great technological importance. The structure of fluorite, AX2, is verified in minerals of the fluorite group (fluorides), the uraninite group (oxides), and four unassigned members. The names applied for minerals and synthetic materials are not always the same. For synthetic compounds with formula A2B2X6Y, the term pyrochlore is applied when the structure is cubic, and the term weberite is applied when the structure is not cubic. For the mineralogical nomenclature, the pyrochlore supergroup includes cubic and trigonal species: the pyrochlore group, where B is Nb; the microlite group, where B is Ta; the roméite group, where B is Sb5 +; and the elsmoreite group, where B is W. In these groups X is dominantly O. Hydrokenoralstonite and fluornatrocoulsellite are two isolated mineral species, where B is Al and Mg, respectively, and X is F. They do not belong to the four quoted mineral groups. Almost all minerals in this supergroup are cubic with space group Fd3m. Hydroxycalciomicrolite is also cubic, but the space group is P4332. Hydrokenomicrolite occurs as cubic and trigonal polytypes, respectively, Fd3m and Rm, and hydrokenoelsmoreite as Fd3m and R. Hydroxykenoelsmoreite occurs as R and fluornatrocoulsellite as Rm. Zirconolite (three polytypes: orthorhombic Acam, trigonal P312, and monoclinic C2/c), weberite (orthorhombic Imma), and ingersonite (trigonal, P312) are not currently included in the pyrochlore supergroup, but they exhibit polytypic relationships with the pyrochlore structure. Murataite-(Y) (cubic F3m), pittongite (hexagonal P6m2), and phyllotungstite (hexagonal P63/mmc) also have structures derived from that of pyrochlore. The compounds known as delta phases have structures derived from fluorite and the formula A4B3X12. Allendeite (trigonal R) is the only mineral representative of these compounds. Fluorite, pyrochlore, and delta phases are all related. As the stoichiometry changes from AX2 to A2B2X6Y to A4B3X12, the anion-to-cation ratio decreases.
... In spite of the correct determination of both the unit cell and symmetry, the structure determination was hindered by the occurrence of complex twinning in the crystals examined. In the course of a research project dealing with the characterization of natural and synthetic Sbbearing oxides ( Bonazzi and Bindi, 2007;Zanazzi et al., 2009;Chelazzi et al., 2011aChelazzi et al., ,b, 2013Bonazzi et al., 2013) we had the chance to test a gem-quality crystal of tegengrenite from the type locality which allowed the superstructure of tegengrenite to be determined. Crystal-chemical considerations also led us to propose a tentative distribution of cations among octahedral and tetrahedral sites. ...
The crystal structure of the spinel-related, Sb mineral tegengrenite from the Filipstad district, Värmland, Sweden, has been solved in the space group R3 [a = 16.0285(9), c = 14.8144(8) Å, V = 3296.1(3) Å3, Z = 42] and refined up to R = 0.0484 for 3589 reflections with F o > 4σ(F o). Tegengrenite exhibits a rhombohedrally distorted spinel-type structure with cations occupying 1/8 of the tetrahedral (T) and 1/2 of the octahedral (M) interstices of a nearly regular cubic close-packing of oxygen atoms. Due to the cation ordering, which leads to a complex superstructure with a unit-cell volume of 21/4 that of a common spinel, the M and T sites of the spinel-type structure split into ten and six independent sites, respectively. Chemical composition determined by electron microprobe led to the empirical formula Mg1.26Mn2+0.85Zn0.04Mn3+0.19Al0.01Si0.12Ti0.03Sb5+0.50O4, on the assumption that no vacancies occur in the mineral (Σcat = 3.00 and Σcharge = 8.00 per formula unit). Crystal-chemical considerations indicate that octahedra are occupied mainly by Mg, Mn3+ and Sb5+ (+Al, + Ti), whereas tetrahedra are filled mainly by Mn2+ and Mg (+Zn) with Si ordered in a specific site. However, the structure refinement shows a low site-scattering factor for one octahedral site, implying substantial vacancies and a larger overall mean Mn valence than stated above. Long mean distances also suggest some Mn2+ on octahedral sites. Together, these observations necessitate the presence of substantial Mn3+ on tetrahedral sites.
... The structure of Ce 2 Zr 2 O 7.97 resembles the cubic pyrochlore, and the negligible rhombohedral distortion (α ¼90.05(6)) is likely due to the redistribution of oxygens in different interstitial sites. Bonazzi et al. have determined the crystal structure of the mineral ingersonite of the ideal formula Ca 2 MnSb 4 O 14 which crystalises in the space group P3 1 21[11]. Although it has the similar lattice constants, a ¼7.282(2) ...
Manganese rare earth antimonates with the formula Mn2Ln3Sb3O14 (Ln=La-Yb and Y) have been prepared and their structures were determined by the Rietveld method using X-ray diffraction data. The compounds with Ln=La, Pr and Nd crystallize in a rhombohedral supercell of the cubic fluorite with the space group and with the lattice parameters ah≈√2ac and ch≈2√3ac, where ac denotes the lattice constant of the cubic fluorite. The structure is pyrochlore-like but differs from the common cubic pyrochlore A2B2O7 in that it consists of fully ordered Mn:Ln in the A sites and Mn:Sb in the B sites with the ratio 1:3. The most interesting feature of Mn2Ln3Sb3O14 is that the divalent Mn ions have different coordination numbers with oxygen and the Mn(II)O6 (octahedron) and Mn(II)O8 (hexagonal bipyramid) alternate along the parent cubic fluorite axes. For medium sized lanthanides, i.e. from Ln=Sm, the rhombohedral phase coexists with the cubic phase and Mn2Y3Sb3O14 is cubic a pyrochlore.
... The structure of Ce 2 Zr 2 O 7.97 resembles the cubic pyrochlore, and the negligible rhombohedral distortion (α ¼90.05(6)) is likely due to the redistribution of oxygens in different interstitial sites. Bonazzi et al. have determined the crystal structure of the mineral ingersonite of the ideal formula Ca 2 MnSb 4 O 14 which crystalises in the space group P3 1 21[11]. Although it has the similar lattice constants, a ¼7.282(2) ...
Manganese rare earth antimonates with the formula Mn(2)Ln(3)Sb(3)O(14) (Ln=La-Yb and Y) have been prepared and their structures were determined by the Rietveld method using X-ray diffraction data. The compounds with Ln=La, Pr and Nd crystallize in a rhombohedral supercell of the cubic fluorite with the space group R (3) over barm and with the lattice parameters a(h) approximate to root 2a(c) and c(h) approximate to root 2 root 3a(c), where a(c) denotes the lattice constant of the cubic fluorite. The structure is pyrochlore-like but differs from the common cubic pyrochlore A(2)B(2)O(7) in that it consists of fully ordered Mn:Ln in the A sites and Mn:Sb in the B sites with the ratio 1:3. The most interesting feature of Mn(2)Ln(3)Sb(3)O(14) is that the divalent Mn ions have different coordination numbers with oxygen and the Mn(II)O-6 (octahedron) and Mn(II)O-8 (hexagonal bipyramid) alternate along the parent cubic fluorite axes. For medium sized lanthanides, i.e. from Ln=Sm, the rhombohedral phase coexists with the cubic phase and Mn2Y3Sb3O14 is cubic a pyrochlore.
... In the Ca-Mn-Sb-O system, two ternary compounds have been described: the binary perovskite Ca 2 Mn 3+ SbO 6 obtained in works [31][32][33][34][35] and the mineral ingersonit Ca 3 Mn 2+ Sb 4 O 14 identified in reference [36] . Ca 3 Mn 2+ Sb 4 O 14 is isostructural with Mn 2 Sb 2 O 7 and has a trigonal 3T-weberite structure. ...
... Among the known M 2þ 2 Sb 2 O 7 oxides, the mineral ingersonite (M 2þ ¼ 3/4Ca þ 1/4Mn), which falls near the transition zone of the two competing structures in the plot of the relative ionicity of the AeO bond versus the R A /R B ratio proposed by Cai e Nino (Fig. 14b in Ref. [28]), crystallizes with the weberite-3T structure [29]. Nevertheless, the pure compounds Ca 2 Sb 2 O 7 and Mn 2þ 2 Sb 2 O 7 , which fall relatively far from the transition zone of the two competing structures in the plot, occur in the two structural types depending on synthesis conditions. ...
... The crystal structure of the orthorhombic Ca 2 Sb 2 O 7 has been recently investigated by in situ X-ray powder diffraction methods within the temperature range 298e1273 K [6]. On the other hand, no data on compressibility of antimonates have been reported in literature so far, except for natural ingersonite, Ca 3 MnSb 4 O 14 [7], which adopts a weberite-3T structure [5]. Under ambient-pressure conditions, Ca 2 Sb 2 O 7 crystallizes as a cubic pyrochlore below 973 K, whereas above this temperature it adopts a weberite-2O structure [8]; moreover, the cubic structure is reported to form by synthesis at pressures higher than 6 GPa [9]. ...
... .0100 (4) (5) .7281 (5) .012 ...
... (4) (5) .7281 (5) .012 (2) .006 ...
An in situ high-pressure X-ray diffraction study has been carried out at room temperature up to 9.23 GPa on a crystal of Ca2Sb2O7 having a weberite-20 structure synthesized by solid-state reaction. A 2nd-order Birch-Murnaghan Equation of State (EoS) was used to refine the pressure-volume data. The refinement of the unit-cell volume and of the isothermal bulk modulus at room pressure leads to: V-0 = 555.8 (1), K-T0 = 154.6 (9) GPa. Unit-cell parameters decrease gradually as a function of pressure with a bulk modulus anisotropy scheme K-a0 > K-b0 > K-c0, with c being the softest direction. The compressional behavior of Ca2Sb2O7 is compared with that shown by ingersonite, Ca3MnSb4O14, a mineral showing a weberite-3T structure.
... Polytypic relationships based on different stacking sequences of the M and N layers are common in both zirconolite-type (Gatehouse et al., 1981;Mazzi and Munno, 1983;Smith and Lumpkin, 1993;Coelho et al., 1997) and weberite-type (Giuseppetti and Tadini, 1978;Yakubovich et al., 1994;Grey and Roth, 2000;Bonazzi and Bindi, 2007) structures. ...
... The driving forces controlling a given compound to crystallize in one of these two competing structural types (i.e., weberite-or zirconolite-type) are still scarcely known. As for weberite-type structures, Cai and Nino (2009) hypothesized that the stabilization of a polytypic variant may be related to the relative size of the A and B cations; among the A 2 2+ Sb 2 O 7 oxides, the mineral ingersonite (A 2+ = 3/4Ca + 1/4Mn - Bonazzi and Bindi, 2007) and the synthetic Mn 2 Sb 2 O 7 (Scott, 1990) crystallize with the weberite-3T structure, while Sr 2 Sb 2 O 7 and CaPbSb 2 O 7 crystallize with the weberite-2O structure (Cai and Nino, 2009 and references therein). According to Ismunandar and Budiman (2002), Pb 2.5 Sb 1.5 O 6.75 adopts a pyrochlore structure at room temperature and transforms to an orthorhombic structure above 1023 K. ...
The crystal structure of synthetic Ca2Sb2O7 has been investigated by in situ X-ray powder diffraction methods within the temperature range 298-1273 K. Ca2Sb2O7 is orthorhombic, space group Imma, over the entire temperature range and shows only general thermal expansion. The unit-cell parameters show a monotonous increase as a function of temperature. Only slight changes occur in the individual bond distances without evidence of abrupt structural changes. The mean coefficients of thermal expansion along the various axes are: alpha(a) = 9.49 x 10(-6)K(-1), alpha(b) = 10.11 x 10(-6) K-1, alpha(c) = 7.56 x 10(-6) K-1 and the bulk thermal expansion coefficient alpha(v) = 27.20 x 10(-6) K-1.
... Numerous phases have been described as rhombohedrally distorted pyrochlores on the basis of their powder diffraction patterns (Subramanian et al. 1983). In a recent review of this subject, however, Bonazzi and Bindi (2007) make the point that the powder patterns of the closely related P-trigonal weberite-type structures can be easily mistaken as corresponding to rhombohedral symmetry. They give the example of the weberite-type mineral ingersonite, Ca 3 MnSb 4 O 14 , for which all the reflections in the reported powder pattern correspond to the R-lattice extinction condition -h + k + l = 3n. ...
Coulsellite, CaNa3AlMg3F14, from the Cleveland tin mine at Luina, western Tasmania, has a rhombohedral distortion of the cubic pyrochlore A(2)B(2)X(6)Y structure, with a = 7.1756(1) angstrom, alpha = 59.867(1)degrees, space group R (3) over barm, Z = 1. The corresponding hexagonal cell parameters are a = 7.1620(1) angstrom, c = 17.5972(3) angstrom. The crystals are multiply twinned about threefold axes of the pseudocubic cell. The structure was determined using X-ray data collected on a twinned crystal and refined to R-obs = 0.027 for 452 observed reflections with I > 2 sigma(I) The structure is possibly unique among published structures of pyrochlore-like minerals in having full 1:3 ordering of Ca:Na in the A sites and Al:Mg in the B sites. Transmission electron photomicrographs show a nanodomain structure due to twinning on a scale of similar to 5 nm.
... Polytypic relationships based on different stacking sequences of the M and N layers are common in both zirconolite-type (Gatehouse et al., 1981;Mazzi and Munno, 1983;Smith and Lumpkin, 1993;Coelho et al., 1997) and weberite-type (Giuseppetti and Tadini, 1978;Yakubovich et al., 1994;Grey and Roth, 2000;Bonazzi and Bindi, 2007) structures. ...
... The driving forces controlling a given compound to crystallize in one of these two competing structural types (i.e., weberite-or zirconolite-type) are still scarcely known. As for weberite-type structures, Cai and Nino (2009) hypothesized that the stabilization of a polytypic variant may be related to the relative size of the A and B cations; among the A 2 2+ Sb 2 O 7 oxides, the mineral ingersonite (A 2+ = 3/4Ca + 1/4Mn - Bonazzi and Bindi, 2007) and the synthetic Mn 2 Sb 2 O 7 (Scott, 1990) crystallize with the weberite-3T structure, while Sr 2 Sb 2 O 7 and CaPbSb 2 O 7 crystallize with the weberite-2O structure (Cai and Nino, 2009 and references therein). According to Ismunandar and Budiman (2002), Pb 2.5 Sb 1.5 O 6.75 adopts a pyrochlore structure at room temperature and transforms to an orthorhombic structure above 1023 K. ...
