Fepo4: Beauty Form And Function: Different Structures

/ Beauty, Form and Function: An Exploration of Symmetry
1 TAN JUN RONG U1510605C
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Writing Exercise – FePO4 Polymorphs
Haines et al., A neutron diffraction study of quartz-type FePO4: high-temperature behavior and α-β phase transition Z. Kristallogr. 218, 193-200 (2003).
Paragraph 1
This writing exercise will be talking about how the structure of FePO4 will change from a low temperature of 294K to a high temperature of 1073K. There is a huge difference in both the cell parameters and atomic coordinates for α phase and β-phase. FePO4 changes from α phase to β-phase at about 980K. This is known as the transition phase. This phase took place at a high-temperature. In α phase, there is a non-linear relationship between the cell parameters and temperature.
When there is a rise of temperature, there will be a rise in the cell parameter and also in its volume and also a decrease in the c/a ratio. Furthermore, the curve part of the bond will increase in size and also rises by a lot. At the temperature of the transition phase which is 980K, the structure will changes from the low-temperature α phase to a high-temperature type of β phase. During β phase, there will be minimum changes in the bond distance and angle in relationship to temperature. When there is a bigger bind distance it will also means there is a higher chance of having dynamic disorder. The whole transition phase is actually related to the tilt angle. When the temperature surpass the transition phase’s temperature of 980K to 1073K, the unit cell structure of Hexagonal β-FePO4 with Fe in the 3d sites (1/2,0,1/2), P at the 3c sites (1/2,0,0) and O in the 12k sites (x,y,z). In a 6-sided unit structure, there are also lattice parameters present. They are a = b ≠ c and α = β = 90°, γ = 120°.
Fig G: Symmetry for different Crystal Structure
Fig F: Relationship between temperature and tilt angle
/ Beauty, Form and Function: An Exploration of
FePO4, a quartz type of iron phosphate, will change its structure under neutron powder diffraction. During this process, the temperature may range from 294K – 1073K. During α phase, the structure is subjected to a low temperature while during β phase, the structure is being exposed to a much higher temperature. Due to the rise in both, it causes the structure in α phase to experience the non-physical behaviour results. The excited low energy, high amplitude vibration in α quartz causes both the temperature and irregularities to rise. In order for the total neutron scattering measurement to be accommodated, there is a need for the effect of this particular disorder. When there is are differences in both the angles and the lengths of bonds being discovered, they are known as tetrahedral distortion. However, when there is a difference in the angle and there is no change in the bond length, then it is known as tetrahedral tilting. During the transition from αβ phase, there is an increase of bridging angles and also a great fall in the tetrahedral tilt angles for the Fe-O-P. This process only take place when the structure is being subjected to about 980K. There is a relationship between the degrees of distortion with the structure of type of β-quartz structure. Furthermore, those two elements mentioned above are also linked to tetrahedral tilt angle δ and the intertetrahedral bridging angle θ. There