Analysis Of Fepo4's A Cation

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This essay will evaluate the Haines et al. Also, the essay will discuss about how the structure of FePO4 will change at various temperature ranging from 294K to 1073K. FePO4's A cation is a transition metal, thus it is not the same as other α-quartz isotopes. FePO4' has α-quartz structure which is tetrahedral when it is at a very low temperature. Under huge pressure, FePO4's structure goes through a phenomena called β-phase which it became a more condensed octahedral structure. Incoherence will be seen during the first order transition. The cell parameters and volume inflates greatly as temperature surges. The increase is not linearly related. The thermal expansion coefficient is calculated as α (K-1)= 2.924 x 10-5 + 2.920 x
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This means that FePO4 will display the arrangement of α- FePO4. This occurs at temperature less than 980K. When the temperature is greater than 980K, it will display the arrangement of β- FePO4. At temperature 294K and 1073K, it will have one formula unit in each of its unit cell. FePo4 will have a trigonal unit cell. Furthermore, β- FePO4 will have a hexagonal unit cell. In the aspect of symmetrical difference, α- FePO4 displayed trigonal symmetry. At the same time, β- FePO4 displayed hexagonal symmetry. The structure in the crystals changes as temperature surges (below 980K). As the temperature surges (below 980K), the cell parameter grows significantly as well. This causes an increase in volume. The enlargement follows a certain direction. This result in c/a ratio to decline as temperature surges. Furthermore, the bent Fe-O-P bond will grow and rise considerably. When the temperature extents to the phase transition value of 980K, The distinguished organisational structure of the low-temperature α phase will work towards the values acquired for high temperature β-quartztype FePO4. α phase will change to β phase. The bond distance and angle would not change drastically when temperature varies in β phase. The distance in Fe-O is about 5.16A. A greater bond distance provides β phase a greater degree of dynamic condition. The tilt angle δ is linked to the α-β transition. This tilt angle δ is utilised for FePO4. The fractional atomic …show more content…
In the structure, it comprises of PO4 tetrahedrons. It serves a significant role in shaping the structural integrity and properties. The tetrahedral distortion comprises of tetrahedral tilt angle δ and inter-tetrahedral bridging angle θ. Both the bond length and the O-PO angle play a part in the tetrahedral distortion when the temperature increases. At the moment, it is more appropriate to identify tetrahedrons as a structured body because the tetrahedral tilt is more essential in contributing to the tetrahedral distortion. In essence, tetrahedral tilt caused tetrahedral distortion. It is measured by tilt angle δ and is dependent on temperature considerably. In the case of quartz-type FePO4, the cell parameters and the volume of the α phase surges significantly and non-linearly when temperature increases. The main cause to the thermal expansion is resulted from angular variations. This is established by the variation in the correlated tilt angles and two symmetrically independent inter-tetrahedral Fe-O-P bridging angles. Hence, the dependence on temperature of thermal expansion is dependent on the angular variations of inter-tetrahedral brdging angles and tetrahedral tilt angles. Using Landau-type model, the temperature dependence of this angle is defined as: δ2 = 2/3 δ02 [1 + (1 – ¾ (T – Tc/T0 – Tc))^1/2]. δ0 is the decline in tilt angle at the transition temperature (980K) and Tc is the

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