FePO4 stands for Iron(III) Phosphate. Although α-FePO4 and β-FePO4 may sound quite similar as they may only differ in terms of the α and β, they β are actually very different in terms of the crystal structures and crystal chemistry of quartz. Based on the research article which was provided in coursera, it states that FePO4 is studied across a range of temperatures ; 294K to 1073K by neutron powder diffraction. The different range in temperature shows different structures. For instance, at significantly lower temperatures, it shows the structure of the α-quartz and at higher temperatures, it shows a β-phase. At lower temperatures, it is tetrahedral, whereas at higher temperatures, it is actually more dense and tends towards an octahedral structure.
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As mentioned previously, the transition temperature for FePO4 is 980K, which is a rather high temperature. To reiterate, α-FePO4 has temperatures less than 980K(from 294K-980K) and for β-FePO4, its temperature is higher than that of 980K. And when this transition occurs, the α-FEPO4 unit cell is trigonal and the β -FEPO4 is a hexagonal unit cell. This is one of the difference between the α-FEPO4 and β -FEPO4 as their symmetrical structure is widely different, with one being trigonal and one being hexagonal. With that being said, both have the same extent of symmetry and the Atoms drawings are rather similar. Furthermore, the rise in temperature shows that the cell parameter will increase greatly, leading to an overall increase in volume. However, as temperature rises up to 980K, there will be a great difference in terms of the structure of the crystals. This would thus lead to a decrease in the c/a ratio as temperature increases, showing an inverse relationship between the two. Hence, when the temperature rises from low (240K) to a high of (980K) the refined structural parameters would thus change from α to β. Adding on, in the β-phase, you may think that there will be a great deal of difference between the bond distance and angle. However, this is not the case. The reason for such is that a larger bond difference would cause a high amount of disorder. This will lead to …show more content…
By knowing these properties, it allows us to find out the structural properties. The structural evolution of this quartz type is called Iron Phosphate, which was observed using neutron powder diffraction which occurs when temperature falls within the range of 294K-1073K. As mentioned previously, the α is a result of lower temperature and β is a result of higher temperatures. The tetrahedral tilt angle δ shows a distortion. Hence, it is not unexpected that this distortion in addition to increasing temperature will lead to vibration, which finally leads to the scattering measurement. This distortion is a result of the difference in angle and length of bonds during tetrahedral tilting. This is also made more significant by the tilt angle and the temperature. However, in this case, there is no change in bond length. The bridging angles between Fe-O-P bridging angles increase and this tetrahedral tilt angles decreases when there is a transition between the α to β, which also shows an increase in temperature up to 980K. for the quartz type FePO4, it shows an increase in the cell parameters and volume of the α phase. In contrast, it is a non-linearly related as a function of temperature. These is actually a result of the dependence of the angular variations and the tetrahedral tilt angles. When the δ value is greater than 22 degrees and θ is less than 136 degrees, the transition from α to β is not observed. As
As mentioned previously, the transition temperature for FePO4 is 980K, which is a rather high temperature. To reiterate, α-FePO4 has temperatures less than 980K(from 294K-980K) and for β-FePO4, its temperature is higher than that of 980K. And when this transition occurs, the α-FEPO4 unit cell is trigonal and the β -FEPO4 is a hexagonal unit cell. This is one of the difference between the α-FEPO4 and β -FEPO4 as their symmetrical structure is widely different, with one being trigonal and one being hexagonal. With that being said, both have the same extent of symmetry and the Atoms drawings are rather similar. Furthermore, the rise in temperature shows that the cell parameter will increase greatly, leading to an overall increase in volume. However, as temperature rises up to 980K, there will be a great difference in terms of the structure of the crystals. This would thus lead to a decrease in the c/a ratio as temperature increases, showing an inverse relationship between the two. Hence, when the temperature rises from low (240K) to a high of (980K) the refined structural parameters would thus change from α to β. Adding on, in the β-phase, you may think that there will be a great deal of difference between the bond distance and angle. However, this is not the case. The reason for such is that a larger bond difference would cause a high amount of disorder. This will lead to …show more content…
By knowing these properties, it allows us to find out the structural properties. The structural evolution of this quartz type is called Iron Phosphate, which was observed using neutron powder diffraction which occurs when temperature falls within the range of 294K-1073K. As mentioned previously, the α is a result of lower temperature and β is a result of higher temperatures. The tetrahedral tilt angle δ shows a distortion. Hence, it is not unexpected that this distortion in addition to increasing temperature will lead to vibration, which finally leads to the scattering measurement. This distortion is a result of the difference in angle and length of bonds during tetrahedral tilting. This is also made more significant by the tilt angle and the temperature. However, in this case, there is no change in bond length. The bridging angles between Fe-O-P bridging angles increase and this tetrahedral tilt angles decreases when there is a transition between the α to β, which also shows an increase in temperature up to 980K. for the quartz type FePO4, it shows an increase in the cell parameters and volume of the α phase. In contrast, it is a non-linearly related as a function of temperature. These is actually a result of the dependence of the angular variations and the tetrahedral tilt angles. When the δ value is greater than 22 degrees and θ is less than 136 degrees, the transition from α to β is not observed. As