Structure
WO3 owns a triclinic structure and its space group and structure type differ depending on the surrounding temperature
| Single cite |
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| pages | 1105-1106 |
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| citeID | Diehl et al. |
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Diehl, R. Brandt, G. Salje, E. (1978) The Crystal Structure of Triclinic WO3. Acta Crystallographica Section B. 34. 1105-1111. https://doi.org/10.1107/S0567740878005014. |
. Different WO3 phases can be observed in temperature range 900-0 °C. In Table 2., there's been presented four main forms of WO3 between temperatures 0 and 900 °C. The information for the table 2 was found by using ICSD. As seen in Table 2. structures of WO3 obtains 8 "formula units" per unit cell under 740 °C. However, above 740 °C the crystal structure of WO3 turns into tetragonal and the amount of "formula units" per unit cell drops down to 2. As WO3 is monoclinic at room temperature, that is the most common structure of WO3.
Table 2. Different structures of tungsten trioxide depending on temperature.
| Temperature (°C) | -50 - 17 | 17 - 330 | 330 - 740 | 740 - 900 |
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Crystal system | Single cite short |
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| pages | 1105-1106 |
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| citeID | Diehl et al. |
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| Triclinic | Monoclinic | Orthorhombic | Tetragonal |
Space group | Single cite short |
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| pages | 1105-1106 |
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| citeID | Diehl et al. |
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| P-1 | P21/n | Pmnb | P4/nmm |
| Structure type | WO3(aP32) | WO3(mP32) | - | WO3(tP8) |
| Coll. code on ICSD | 135341 | 8654 | 836 | 88367 |
| Formula units, Z | 8 | 8 | 8 | 2 |
| Cell parameters a, b, c (Å) | 7.308, 7.525, 7.686 | 7.343, 7.624, 7.716 | 7.341, 7.570, 7.754 | 5.303, 5.303, 3.935 |
| Cell parameters α, β, γ (°) | 89.021, 90.865, 90.753 | 90.000, 90.233, 90.000 | 90.000, 90.000, 90.000 | 90.000, 90.000, 90.000 |
In Figure 1. is presented the structure of WO3 in under 17 °C where its crystal system is triclinic.
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Figure 1. The structures of WO3(aP32) (Figure: Eino Kilpeläinen)
In Figure 2. is shown the most common structure of WO3 because monoclinic crystal system appears in room temperature.
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Figure 2. The structures of WO3(mP32) (Figure: Eino Kilpeläinen)
When temperature is between 330 and 740 °C, WO3 have an orthorhombic crystal system as seen in Figure 3.
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Figure 3. The structures of orthorhombic WO3. (Figure: Eino Kilpeläinen)
When temperature is increased to 740-900 °C, the crystal system changes quite radically into tetragonal and its number of formula units drops form 8 to 2 as shown in Figure 4.
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Figure 4. The structures of WO3(tP8). (Figure: Eino Kilpeläinen)