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V2O5 is a binary transition metal oxide with the highest oxidation state (+V) among vanadium oxides. At room temperature, this oxide is an odorless solid crystalline powder whose color varies from pale yellow to dark orange depending on its state of division (Figure 1)[1][2]. V2O5 is hazardous for health and environment, but it has properties that are used in many industry applications, such as a cathode in lithium-ion batteries[2][3], a component in special glasses[4], and a catalyst in the production of various acids such as sulfuric[1][5]. And although this is only a part of all possible applications, vanadium pentoxide has found the greatest distribution (about 85% of all world vanadium) in the production of springs and cutting-tool steels, where it is mixed with Fe2O3 and Al to increase their toughening[1][6].


Vanadium pentoxide can be obtained in several ways, for example, by heating metallic vanadium in oxygen under pressure as shown in following equation:

4 V + 5 O2 → 2 V2O5

However, this method does not produce the purest vanadium pentoxide, since in addition to V2O5, other vanadium oxides are formed during this heating, which are difficult to separate from each other[7].

Another method is to calcinate other vanadium oxides such as VO, V2O3 and VO2 in oxygen as shown in the example below[8]

4 VO2 + O2 → 2 V2O5

The purest V2O5 is obtained by a multi-step reaction. First, vanadium slag is mixed with NaCl and roasted, which leads to the oxidation of vanadium to form V(V) and the formation of sodium vanadate. Further, with the help of sulfuric acid, the pH is lowered, which leads to the formation of sodium polyvanadate Na4H2V10O28. An increase in temperature triggers the hydrolysis of sodium polyvanadate, which leads to the precipitation of a phase called "red cake" (Figure 2) due to the characteristic reddish color:

6 Na4H2V10O28 + 7 H2SO4 + (n+13) H2O 5 Na2V12O31 · n H2O + 7 Na2SO4+13 H2O

Next, the "red cake" is dissolved in sodium hydroxide, which leads to an increase in pH, and NH4Cl is added, which leads to the precipitation of ammonium metavanadate:

VO3- + NH4+ NH4VO3

Finally, the ammonium metavanadate is calcined, resulting in V2O5 with a purity of about 98.5%[6][8]:

2 NH4VO3 → V2O5 + NH3 + H2O


At ambient pressure, vanadium pentoxide crystallizes in the orthorhombic crystal system[2][9][10], however, there are also reports of the existence of monoclinic V2O[11][12]. The difference between the methods for obtaining an orthorhombic and monoclinic structure is that a much higher pressure (about 2-6 GPa) is required to obtain a monoclinic structure, which allows the orthorhombic structure to be reformed into a denser form. Alternatively, there is another method to obtain monoclinic V2O5, namely by adding sufficient oxygen deficiencies to the crystal structure[13]. Below are images of V2O5 crystal structures in the orthorhombic system (Figs. 3 and 4) and in the monoclinic system (Figs. 5 and 6). As can be seen from these figures, the difference between these systems, in addition to the unit cell parameters and crystal symmetry, lies in different polyhedra.

It should be noted that in the ICSD data for the orthorhombic structure from which the figures below are made, in addition to five V-O bonds, there is also a sixth bond with a length significantly longer than the rest (2.81 Å versus 2.02 Å), which makes the polyhedra octahedral. Earlier studies pointed to the presence of this bond in the structure[9], however, later studies have shown that this bond is actually a weak interaction, and polyhedra are in fact square pyramids with common corners and edges[10]. Thus, if the orthorhombic structure is viewed from a greater distance (Fig. 4), it is possible to see that it forms two-dimensional nets.

Figure 3. Close-up structure of orthorhombic V2O5 (Data from ICSD, visualized with VESTA. Figures: Nikita Jamkin).

Figure 4. Distant orthorhombic V2O5 structure (Data from ICSD, visualized with VESTA. Figures: Nikita Jamkin).

In turn, the structure of monoclinic V2O5 (here δ-V2O5[11]) is a three-dimensional structure, in which the polyhedra are in the form of distorted octahedrons with the central atom displaced towards the edge, and form paired zigzag chains connected by common corners and, in some places, by common edges.

Figure 5. Close-up structure of monoclinic V2O5 (Data from ICSD, visualized with VESTA. Figures: Nikita Jamkin).

Figure 6. Distant structure of monoclinic V2O5 (Data from ICSD, visualized with VESTA. Figures: Nikita Jamkin).


The magnetic nature of V2O5 requires more detailed studies. At the moment, it is believed that the bulk phase of V2O5 is diamagnetic, since V5+ ions do not have unpaired electrons and, therefore, have a balanced spin equal to zero, which, in turn, means that V2O5 does not have its own magnetic moment[14]. On the other hand, some practical studies show that V2O5 is a paramagnet mainly due to oxygen vacancies present in the structure, and an increase in the number of oxygen vacancies can even lead to antiferromagnetism under certain conditions[13].

It is mainly due to oxygen vacancies that V2O5 can be used as an n-type semiconductor, since a decrease in the amount of oxygen in the lattice will lead to an increase in the number of charge carriers[15]. Below is Figure 7, according to which V2O5 is a wide-gap semiconductor with an indirect band gap of 2.3 eV.

Figure 7. V2Oband structure (License: CC BY)[16]

Moreover, due to its high oxidation state, V2O5 is an amphoteric compound and, depending on the environment, behaves like a base or an acid and therefore is also highly soluble in acids and bases[17], but in addition to this, and unlike most other metal oxides, it is slightly soluble in water[7][18].

Finally, powder X-ray diffraction patterns of both V2O5 crystal systems using CuKα radiation are presented below (Fig. 8).

Figure 8. Powder XRD patterns for orthorhombic (left, license: CC BY)[19] and monoclinic (right; calculated data from ICSD, Figure: Nikita Jamkin) V2O5 systems.


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Изображение молекулярной модели

Figure 1. V2O5 powder (License: CC BY-SA 3.0)[20].


Figure 2. "Red cake" (License: CC BY-SA 3.0)[21].

Properties of orthorhombic V2O5[22]

Molar mass181.88 g/mol

3.35 g/cm3, (4.16 g/cm3 for monoclinic[11])

Water solubility0.7 g/L (20 °C)
Melting point681 °C
Boiling point1750 °C (decomposes)


Structural properties of V2O5[11][10]

Crystal systemOrthorhombicMonoclinic
ICSD No.60767156052
Space group

Pmmn (No. 59)

C2/c (No. 15)
Unit cell dimensions

a=11.512 Å, b=4.368 Å,  c=3.564 Å

α=90°, β=90°, γ=90°

a=11.972 Å, b=4.702 Å, c=5.325 Å

α=90°, β=104.41°, γ=90°

Unit cell volume179 Å3300 Å3
Formula units per unit cell24
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