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A new approach is proposed to determine unambiguously the location of four cations within the crystal structure of a natural AB2O6 columbite-type compound and derivatives, when submitted to order-disorder transitions caused by heat treatments. This method is based on the successive use of electron microprobe analysis to determine the cation concentration, Mössbauer spectroscopy to identify the Fe occupation, and a crystal structure determination of the samples combining Rietveld refinements of both neutron and X-ray diffraction. This approach is tested successfully to investigate (Fe, Mn, Nb, Ta) natural minerals as well as oxides obtained by heat treatment of the initial AB2O6 columbite-type compound.
Supporting information
| Crystallographic Information File (CIF) https://doi.org/10.1107/S0021889811023211/cg5181sup1.cif Contains datablocks global, Columbite |
| Rietveld powder data file (CIF format) https://doi.org/10.1107/S0021889811023211/cg5181fig05sup2.rtv Contains datablock Columbite |
| Crystallographic Information File (CIF) https://doi.org/10.1107/S0021889811023211/cg5181sup3.cif Contains datablocks global, Columbite |
| Rietveld powder data file (CIF format) https://doi.org/10.1107/S0021889811023211/cg5181fig06sup4.rtv Contains datablock Columbite |
| Crystallographic Information File (CIF) https://doi.org/10.1107/S0021889811023211/cg5181sup5.cif Contains datablocks global, Columbite, Rutile |
| Rietveld powder data file (CIF format) https://doi.org/10.1107/S0021889811023211/cg5181fig07sup6.rtv Contains datablock Columbite |
| Crystallographic Information File (CIF) https://doi.org/10.1107/S0021889811023211/cg5181sup7.cif Contains datablocks global, Columbite, Rutile |
| Rietveld powder data file (CIF format) https://doi.org/10.1107/S0021889811023211/cg5181fig08sup8.rtv Contains datablock Columbite |
| Crystallographic Information File (CIF) https://doi.org/10.1107/S0021889811023211/cg5181sup9.cif Contains datablocks global, Wodginite, Nb2O5, Nb2O5_monoclinic |
| Rietveld powder data file (CIF format) https://doi.org/10.1107/S0021889811023211/cg5181fig09sup10.rtv Contains datablock Wodginite |
| Crystallographic Information File (CIF) https://doi.org/10.1107/S0021889811023211/cg5181sup11.cif Contains datablocks global, Wodginite, Ta2O5_C2mm, Nb2O5 |
| Rietveld powder data file (CIF format) https://doi.org/10.1107/S0021889811023211/cg5181fig10sup12.rtv Contains datablock Wodginite |
Program(s) used to refine structure: FULLPROF.
Crystal data top
? | c = 5.0938 (8) Å |
Mr = ? | V = 407.95 (11) Å3 |
Orthorhombic, Pbcn | Z = ? |
Hall symbol: -P 2n 2ab | Constant Wavelength Neutron Diffraction radiation, λ = 1.280000 Å |
a = 14.097 (2) Å | ?, ? × ? × ? mm |
b = 5.6815 (9) Å | |
Data collection top
Radiation source: nuclear reactor | 2θmin = 8.148°, 2θmax = 87.948°, 2θstep = 0.200° |
Refinement top
Rp = 2.278 | 400 data points |
Rwp = 3.185 | 28 parameters |
Rexp = 0.612 | 0 restraints |
RBragg = 8.472 | |
χ2 = NOT FOUND | |
Crystal data top
? | c = 5.0938 (8) Å |
Mr = ? | V = 407.95 (11) Å3 |
Orthorhombic, Pbcn | Z = ? |
a = 14.097 (2) Å | Constant Wavelength Neutron Diffraction radiation, λ = 1.280000 Å |
b = 5.6815 (9) Å | ?, ? × ? × ? mm |
Data collection top
2θmin = 8.148°, 2θmax = 87.948°, 2θstep = 0.200° | |
Refinement top
Rp = 2.278 | χ2 = NOT FOUND |
Rwp = 3.185 | 400 data points |
Rexp = 0.612 | 28 parameters |
RBragg = 8.472 | 0 restraints |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | Occ. (<1) |
O1 | 0.0899 (10) | 0.110 (3) | 0.0624 (14) | 0.0065 (6)* | |
O2 | 0.4225 (10) | 0.111 (3) | 0.0878 (18) | 0.0065 (6)* | |
O3 | 0.7583 (9) | 0.1330 (13) | 0.1017 (15) | 0.0065 (6)* | |
FeA | 0.00000 | 0.342 (7) | 0.25000 | 0.0135 (8)* | 0.33000 |
MnA | 0.00000 | 0.342 (7) | 0.25000 | 0.0135 (8)* | 0.24 (3) |
TaA | 0.00000 | 0.342 (7) | 0.25000 | 0.0135 (8)* | 0.43 (3) |
NbA | 0.00000 | 0.342 (7) | 0.25000 | 0.0135 (8)* | 0.00000 |
FeB | 0.166 (2) | 0.167 (3) | 0.750 (5) | 0.0135 (8)* | 0.13500 |
MnB | 0.166 (2) | 0.167 (3) | 0.750 (5) | 0.0135 (8)* | 0.082 (16) |
TaB | 0.166 (2) | 0.167 (3) | 0.750 (5) | 0.0135 (8)* | 0.433 (16) |
NbB | 0.166 (2) | 0.167 (3) | 0.750 (5) | 0.0135 (8)* | 0.35000 |
Experimental details
Crystal data |
Chemical formula | ? |
Mr | ? |
Crystal system, space group | Orthorhombic, Pbcn |
Temperature (K) | ? |
a, b, c (Å) | 14.097 (2), 5.6815 (9), 5.0938 (8) |
V (Å3) | 407.95 (11) |
Z | ? |
Radiation type | Constant Wavelength Neutron Diffraction, λ = 1.280000 Å |
Specimen shape, size (mm) | ?, ? × ? × ? |
|
Data collection |
Diffractometer | ? |
Specimen mounting | ? |
Data collection mode | ? |
Scan method | ? |
2θ values (°) | 2θmin = 8.148 2θmax = 87.948 2θstep = 0.200 |
|
Refinement |
R factors and goodness of fit | Rp = 2.278, Rwp = 3.185, Rexp = 0.612, RBragg = 8.472, χ2 = NOT FOUND |
No. of data points | 400 |
No. of parameters | 28 |
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