Differences Of Iron (III) Phosphate

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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. …show more content…
This thermal expansion is given by (K-1)= 2.924 x 10-5 + 2.920 x10-10 ( T-300)2. There are several factors that causes the change in the thermal expansion. The main ones being the angular variations of the FE-O-P bridging angles increase and the tetrahedral tilt angles decrease greatly as the temperature of 980k is reached. This volumetric reliance on temperature is caused by the average δ and θ angles. To add on, the FE-O distance has an inverse relationship with temperature and with that being said, it shows a similarity with the Si-O distance and an α-quartz. These can actually be explained due to the rising temperature as a result of low-energy and great amount of vibrations. The formula: δ2= 2/3 δ02 [1 + (1 – ¾ (T – Tc/T0 – Tc))^1/2], shows the temperature dependence of this tilt angle. This overall tilt angle is the sum of individual tilt angles. The above formula shows that δ0 is the decrease in tilt angle at the transition temperature (980K) and Tc on the other hand, is the temperature for the second-order transition. Hence, this shows that the behaviour of Iron(III) Phosphate and the α-quartz has no similarities and resemblance with regards to the homeotypes, and the reason for this is because the δ angle decreases at a faster rate than the …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

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