Haines et al., A neutron diffraction study of quartz-type FePO4: high-temperature behavior and αβ phase transition Kristallogr. 218, 193-200 (2003)
Paragraph 1 Crystal chemical relationship between quartz (SiO2) and FePO4
Silicon dioxide is an oxide of silicon with the chemical formula of SiO2. SiO2 is a chemical compound most commonly found in Quartz and it has a space group of P3121. The lattice symmetry of SiO2 is tetrahedron, where there are 4 oxygen atoms covalently bonded to the silicon atom, as shown in Figure 1. Figure 1 - Structure of Silicon dioxide
Iron (III) phosphate is a compound with the chemical formula of FePO4. FePO4 commonly has two polymorphs which are α-FePO4 and β-FePO4. α- FePO4 is the most common form of the compound …show more content…
This will add up to a total charge of +8 which is represented by 2 silicon ions with a charge of +4 in silicon dioxide.
The equation shows a similarity in the crystal chemical relationship between α-FePO4 and SiO2 and thus, we can expect to observe similar lattice symmetry and space groups between the two.
Since we know that if we heat up SiO2, we will expect to observe an α-β transition, and from the above we have already proven that the two compounds are in fact similar in terms of crystal chemistry, we can also expect to observe a transition from α-FePO4, to …show more content…
In this part, we will go more deeply into this symmetry relationship between the two polymorphs and the dependence on temperature.
The space symmetry and lattice symmetry between the FePO4 polymorphs will change progressively with a change in temperature, and at a temperature of 980K is where the transition starts to occur.
We will observe this transition between the polymorphs at a temperature range of 274K and 1073K. This transition between the two polymorphs is a first order transition and this happens at a temperature of about 980K. As the temperature increases from 274K, there is a non-linear increase in unit cell volume, which can be deduced from the space group that α- FePO4 belongs to, which is P3121.
We can attribute this increase in unit cell volume to the tilting in the tetrahedral lattice structure (this will be explained further in paragraph 3).
This can be shown in Figure 2 and Figure 3 below where the structure of α-FePO4 is obviously more compact than β-FePO4, and the unit cell volume of the former is significantly smaller than the
Paragraph 1 Crystal chemical relationship between quartz (SiO2) and FePO4
Silicon dioxide is an oxide of silicon with the chemical formula of SiO2. SiO2 is a chemical compound most commonly found in Quartz and it has a space group of P3121. The lattice symmetry of SiO2 is tetrahedron, where there are 4 oxygen atoms covalently bonded to the silicon atom, as shown in Figure 1. Figure 1 - Structure of Silicon dioxide
Iron (III) phosphate is a compound with the chemical formula of FePO4. FePO4 commonly has two polymorphs which are α-FePO4 and β-FePO4. α- FePO4 is the most common form of the compound …show more content…
This will add up to a total charge of +8 which is represented by 2 silicon ions with a charge of +4 in silicon dioxide.
The equation shows a similarity in the crystal chemical relationship between α-FePO4 and SiO2 and thus, we can expect to observe similar lattice symmetry and space groups between the two.
Since we know that if we heat up SiO2, we will expect to observe an α-β transition, and from the above we have already proven that the two compounds are in fact similar in terms of crystal chemistry, we can also expect to observe a transition from α-FePO4, to …show more content…
In this part, we will go more deeply into this symmetry relationship between the two polymorphs and the dependence on temperature.
The space symmetry and lattice symmetry between the FePO4 polymorphs will change progressively with a change in temperature, and at a temperature of 980K is where the transition starts to occur.
We will observe this transition between the polymorphs at a temperature range of 274K and 1073K. This transition between the two polymorphs is a first order transition and this happens at a temperature of about 980K. As the temperature increases from 274K, there is a non-linear increase in unit cell volume, which can be deduced from the space group that α- FePO4 belongs to, which is P3121.
We can attribute this increase in unit cell volume to the tilting in the tetrahedral lattice structure (this will be explained further in paragraph 3).
This can be shown in Figure 2 and Figure 3 below where the structure of α-FePO4 is obviously more compact than β-FePO4, and the unit cell volume of the former is significantly smaller than the