The space group for α-FePO4 is P3121, with the lattice symmetry being tetrahedral in shape. On the other hand, the space group for β-FePO4 is P6422, with the lattice symmetry being hexagonal in shape.
In this writing assignment, FePO4 is studied at varying temperature ranging from 294K to
1073K by neutron powder diffraction. At a relatively low temperature, it adopts the structure of the α-quartz. However, at high pressures, it changes and it can be observed that it becomes a denser octahedral structure due to a phase change occurring, which is also known as the β-phase. This transition occurs and can be observed at the temperature of 980K.
During the first-order transition, for α-phase, the cell parameters increases significantly as …show more content…
Tetrahedral distortion is the change in which both the angles and the length of the bonds are present while in tetrahedral tilting, there is only a change in the angle and notably, there is no change in the bond length.
When approaching the α-β transition at 980K, the Fe-O-P bridging angles increase and the tetrahedral tilt angles does the opposite – it decreases to a great extent. The degree of distortion with respect to β-quartz structure type can be related to the tetrahedral tilt angle σ as well as the intertetrahedral bridging angle θ. However, if the σ value is greater than 22 degrees and the θ value is less than 136 degrees, the α-β transition is not commonly observed in most materials. However, the structural parameters of FePO4 lie close to the above limiting values.
As the temperature increases from 294K to 969K, it is observed that Fe-O2 decreases in length and the angle of Fe-O2 also becomes smaller along with the decrease in the bond length. This eventually results in a change in unit cell size and volume. Similarly, in P-O4, an increase in temperature results in a decrease in bond length and the bond angle drops
In this writing assignment, FePO4 is studied at varying temperature ranging from 294K to
1073K by neutron powder diffraction. At a relatively low temperature, it adopts the structure of the α-quartz. However, at high pressures, it changes and it can be observed that it becomes a denser octahedral structure due to a phase change occurring, which is also known as the β-phase. This transition occurs and can be observed at the temperature of 980K.
During the first-order transition, for α-phase, the cell parameters increases significantly as …show more content…
Tetrahedral distortion is the change in which both the angles and the length of the bonds are present while in tetrahedral tilting, there is only a change in the angle and notably, there is no change in the bond length.
When approaching the α-β transition at 980K, the Fe-O-P bridging angles increase and the tetrahedral tilt angles does the opposite – it decreases to a great extent. The degree of distortion with respect to β-quartz structure type can be related to the tetrahedral tilt angle σ as well as the intertetrahedral bridging angle θ. However, if the σ value is greater than 22 degrees and the θ value is less than 136 degrees, the α-β transition is not commonly observed in most materials. However, the structural parameters of FePO4 lie close to the above limiting values.
As the temperature increases from 294K to 969K, it is observed that Fe-O2 decreases in length and the angle of Fe-O2 also becomes smaller along with the decrease in the bond length. This eventually results in a change in unit cell size and volume. Similarly, in P-O4, an increase in temperature results in a decrease in bond length and the bond angle drops