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The phase designated γ-Zn3(VO4)2 reported as a minor second phase in zinc oxide-based varistor materials doped with vanadium oxide and manganese oxide is shown to be the L phase, (Zn1 − xMnx)2V2O7 (0.188 < x < 0.538), in the pseudo-binary Mn2V2O7–Zn2V2O7 system. Analysis of X-ray powder diffraction patterns and electron diffraction patterns of this phase shows that the previously published a, c and β values for this thortveitite-related phase are incorrect. Instead, Rietveld refinement of the X-ray powder pattern of the L phase shows that it has a monoclinic C lattice with Z = 6, with a = 10.3791 (1), b = 8.5557 (1), c = 9.3539 (1) Å and β = 98.467 (1)°. Although prior convergent-beam electron diffraction work of `γ-Zn3(VO4)2' confirmed the C Bravais lattice, the space group was found to be Cm rather than C2/m, the difference perhaps arising from the inability of the X-rays to detect small displacements of oxygen. Attempts to refine the structure in Cm did not produce improved R factors. The relationship between the crystal structure of the L phase and the high-temperature C2/m β′-Zn2V2O7 thortveitite-type solid solution is discussed.
Supporting information
Crystal data top
Mn0.6O7V2Zn1.4 | V = 821.58 (2) Å3 |
Mr = 338.37 | Z = 6 |
Monoclinic, C2/m | Dx = 4.10 Mg m−3 |
a = 10.37908 (11) Å | Cu Kα radiation, λ = 1.5418 Å |
b = 8.55572 (9) Å | T = 298 K |
c = 9.35394 (10) Å | black-brown |
β = 98.4667 (9)° | flat sheet, 20 × 20 mm |
Data collection top
Bruker D8 diffractometer | 2θmin = 7.986°, 2θmax = 157.980°, 2θstep = 0.018° |
Refinement top
Rp = 0.076 | ? data points |
Rwp = 0.099 | 53 parameters |
Rexp = 0.075 | (Δ/σ)max = 0.001 |
R(F) = 0.032 | Background function: One on X 1172.905
Chebychev polynomial, Coefficient 0 58.91392
1 37.15686
2 1.077047
3 11.79921
4 -2.054791
5 -3.935534
6 5.044208
7 -0.2344829
8 1.70655
9 0.434558
10 2.996575 |
χ2 = 1.322 | |
Crystal data top
Mn0.6O7V2Zn1.4 | β = 98.4667 (9)° |
Mr = 338.37 | V = 821.58 (2) Å3 |
Monoclinic, C2/m | Z = 6 |
a = 10.37908 (11) Å | Cu Kα radiation, λ = 1.5418 Å |
b = 8.55572 (9) Å | T = 298 K |
c = 9.35394 (10) Å | flat sheet, 20 × 20 mm |
Data collection top
Bruker D8 diffractometer | 2θmin = 7.986°, 2θmax = 157.980°, 2θstep = 0.018° |
Refinement top
Rp = 0.076 | χ2 = 1.322 |
Rwp = 0.099 | ? data points |
Rexp = 0.075 | 53 parameters |
R(F) = 0.032 | |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Biso*/Beq | Occ. (<1) |
Zn1 | 0.3463 (2) | 0.8183 (2) | 0.20169 (19) | 0.24 (4)* | 0.7 |
Zn2 | 0 | 0.8210 (4) | 0.5 | 0.24 (4)* | 0.7 |
V1 | 0.0496 (3) | 0 | 0.1870 (4) | 0.01 (3)* | |
V2 | 0.3732 (3) | 0 | 0.8855 (3) | 0.01 (3)* | |
V3 | 0.6933 (4) | 0 | 0.4888 (4) | 0.01 (3)* | |
O1a | 0.3838 (10) | 0 | 0.6859 (10) | 0.17 (6)* | |
O1b | 0 | 0 | 0 | 0.17 (6)* | |
O2a | 0.0017 (7) | 0.1663 (10) | 0.7449 (7) | 0.17 (6)* | |
O2b | 0.2812 (8) | 0.1537 (9) | 0.8906 (7) | 0.17 (6)* | |
O2c | 0.3497 (8) | 0.1652 (9) | 0.4243 (7) | 0.17 (6)* | |
O3a | 0.1349 (11) | 0 | 0.5033 (11) | 0.17 (6)* | |
O3b | 0.4402 (13) | 0 | 0.1005 (11) | 0.17 (6)* | |
O3c | 0.2153 (13) | 0 | 0.2048 (11) | 0.17 (6)* | |
Mn1 | 0.3463 (2) | 0.8183 (2) | 0.20169 (19) | 0.24 (4)* | 0.3 |
Mn2 | 0 | 0.8210 (4) | 0.5 | 0.24 (4)* | 0.3 |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Zn1 | 0.00306 | 0.00306 | 0.00306 | 0.000000 | 0.000000 | 0.000000 |
Zn2 | 0.00306 | 0.00306 | 0.00306 | 0.000000 | 0.000000 | 0.000000 |
V1 | 0.00013 | 0.00013 | 0.00013 | 0.000000 | 0.000000 | 0.000000 |
V2 | 0.00013 | 0.00013 | 0.00013 | 0.000000 | 0.000000 | 0.000000 |
V3 | 0.00013 | 0.00013 | 0.00013 | 0.000000 | 0.000000 | 0.000000 |
O1a | 0.00210 | 0.00210 | 0.00210 | 0.000000 | 0.000000 | 0.000000 |
O1b | 0.00210 | 0.00210 | 0.00210 | 0.000000 | 0.000000 | 0.000000 |
O2a | 0.00210 | 0.00210 | 0.00210 | 0.000000 | 0.000000 | 0.000000 |
O2b | 0.00210 | 0.00210 | 0.00210 | 0.000000 | 0.000000 | 0.000000 |
O2c | 0.00210 | 0.00210 | 0.00210 | 0.000000 | 0.000000 | 0.000000 |
O3a | 0.00210 | 0.00210 | 0.00210 | 0.000000 | 0.000000 | 0.000000 |
O3b | 0.00210 | 0.00210 | 0.00210 | 0.000000 | 0.000000 | 0.000000 |
O3c | 0.00210 | 0.00210 | 0.00210 | 0.000000 | 0.000000 | 0.000000 |
Mn1 | 0.00306 | 0.00306 | 0.00306 | 0.000000 | 0.000000 | 0.000000 |
Mn2 | 0.00306 | 0.00306 | 0.00306 | 0.000000 | 0.000000 | 0.000000 |
Geometric parameters (Å, º) top
Zn1—O2bi | 2.035 (8) | V1—O2aviii | 1.677 (8) |
Zn1—O2ai | 2.049 (8) | V1—O3c | 1.704 (14) |
Zn1—O3cii | 2.068 (9) | V1—O1b | 1.7495 |
Zn1—O2ciii | 2.082 (7) | V2—O2b | 1.630 (8) |
Zn1—O3bii | 2.130 (9) | V2—O2bix | 1.630 (8) |
Zn2—O3aii | 2.073 (8) | V2—O1a | 1.887 (10) |
Zn2—O3aiv | 2.073 (8) | V2—O3bx | 1.922 (13) |
Zn2—O2cv | 2.094 (8) | V2—O3bxi | 2.028 (10) |
Zn2—O2ci | 2.094 (8) | V3—O1ax | 1.710 (9) |
Zn2—O2avi | 2.291 (7) | V3—O2cx | 1.722 (8) |
Zn2—O2aiii | 2.291 (7) | V3—O2cxii | 1.722 (8) |
V1—O2avii | 1.677 (8) | V3—O3ax | 1.774 (12) |
| | | |
O2ai—Zn1—O2bi | 95.4 (2) | O2aviii—V1—O2avii | 116.1 (6) |
O3cii—Zn1—O2ai | 163.3 (3) | O3c—V1—O2aviii | 109.6 (3) |
O3cii—Zn1—O2bi | 98.0 (2) | O3c—V1—O2avii | 109.6 (3) |
O2ciii—Zn1—O3cii | 81.3 (3) | O1b—V1—O3c | 104.0 (4) |
O2ciii—Zn1—O2ai | 84.3 (2) | O1b—V1—O2aviii | 108.5 (2) |
O2ciii—Zn1—O2bi | 112.7 (2) | O1b—V1—O2avii | 108.5 (2) |
O3bii—Zn1—O2ciii | 117.0 (3) | O2bix—V2—O2b | 107.6 (6) |
O3bii—Zn1—O3cii | 78.6 (4) | O1a—V2—O2bix | 98.5 (2) |
O3bii—Zn1—O2ai | 100.7 (4) | O1a—V2—O2b | 98.5 (2) |
O3bii—Zn1—O2bi | 128.9 (3) | O3bx—V2—O1a | 82.1 (4) |
O3aiv—Zn2—O3aii | 84.7 (5) | O3bx—V2—O2bix | 125.9 (3) |
O2cv—Zn2—O3aiv | 89.9 (2) | O3bx—V2—O2b | 125.9 (3) |
O2cv—Zn2—O3aii | 160.6 (3) | O3bxi—V2—O3bx | 74.8 (6) |
O2ci—Zn2—O2cv | 100.9 (5) | O3bxi—V2—O1a | 156.9 (5) |
O2ci—Zn2—O3aiv | 160.6 (3) | O3bxi—V2—O2bix | 95.1 (3) |
O2ci—Zn2—O3aii | 89.9 (2) | O3bxi—V2—O2b | 95.1 (3) |
O2avi—Zn2—O2ci | 105.3 (3) | O2cx—V3—O1ax | 109.5 (2) |
O2avi—Zn2—O2cv | 78.3 (3) | O2cxii—V3—O2cx | 110.4 (5) |
O2avi—Zn2—O3aiv | 92.5 (3) | O2cxii—V3—O1ax | 109.5 (2) |
O2avi—Zn2—O3aii | 83.4 (3) | O3ax—V3—O2cxii | 108.0 (3) |
O2aiii—Zn2—O2avi | 174.6 (4) | O3ax—V3—O2cx | 108.0 (3) |
O2aiii—Zn2—O2ci | 78.3 (3) | O3ax—V3—O1ax | 111.4 (5) |
O2aiii—Zn2—O2cv | 105.3 (3) | V2—O1a—V3x | 149.1 (6) |
O2aiii—Zn2—O3aiv | 83.4 (3) | V1—O1b—V1xiii | 180.000 |
O2aiii—Zn2—O3aii | 92.5 (3) | | |
Symmetry codes: (i) −x+1/2, y+1/2, −z+1; (ii) x, y+1, z; (iii) x, −y+1, z; (iv) −x, y+1, −z+1; (v) x−1/2, y+1/2, z; (vi) −x, −y+1, −z+1; (vii) −x, y, −z+1; (viii) −x, −y, −z+1; (ix) x, −y, z; (x) −x+1, y, −z+1; (xi) x, y, z+1; (xii) −x+1, −y, −z+1; (xiii) −x, y, −z. |
Experimental details
Crystal data |
Chemical formula | Mn0.6O7V2Zn1.4 |
Mr | 338.37 |
Crystal system, space group | Monoclinic, C2/m |
Temperature (K) | 298 |
a, b, c (Å) | 10.37908 (11), 8.55572 (9), 9.35394 (10) |
β (°) | 98.4667 (9) |
V (Å3) | 821.58 (2) |
Z | 6 |
Radiation type | Cu Kα, λ = 1.5418 Å |
Specimen shape, size (mm) | Flat sheet, 20 × 20 |
|
Data collection |
Diffractometer | Bruker D8 diffractometer |
Specimen mounting | ? |
Data collection mode | ? |
Scan method | ? |
2θ values (°) | 2θmin = 7.986 2θmax = 157.980 2θstep = 0.018 |
|
Refinement |
R factors and goodness of fit | Rp = 0.076, Rwp = 0.099, Rexp = 0.075, R(F) = 0.032, χ2 = 1.322 |
No. of data points | ? |
No. of parameters | 53 |
No. of restraints | ? |
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