The Incructural Reflection Of The Structural Evolution Of Fepo4

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The structural evolution of FePO4 studied from a temperature range of 294K to 1073K by neutron powder diffraction. It is unique from α-quartz isotopes. It is different because it’s a cation is a transition metal. The structure dimensions and atomic coordinates in the α phase tend to increase by great amounts as the high-temperature β-phase rises and exhibit first order transition at 980K. The atomic structure dimensions of the α-phase FePO4 increased in a non-uniform pattern with respect to temperature. A thermal expansion coefficient α (K-1)= 2.924 x 10-5 + 2.920 x 10-10 ( T-300)2 is used to get its volume results. Angular variations caused by the changes in the 2 symmetrically-independent Fe-O-P bridging angles as well as
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From the table, it is clear that as the temperature increases which are below 980K, the crystals starts to show changes. The cell dimensions increases with the temperature, which causes a rise in volume. There is preferential expansion along a direction, so the c/a ratio will decrease as temperature increases. From 980K to 1073K, unit cell structure is 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 Hexagonal unit structure, the lattice parameters are as follows: a = b ≠ c and α = β = 90°, γ = 120°. By comparing the cells at different temperatures, it shows that the tilt angles decrease when temperature increases. The lattice parameters in the Trigonal unit structures are: a = b = c and α = β = γ ≠ 90°. By comparison with the symmetrical relationship between the Trigonal α-FePO4 and Hexagonal β-FePO4, it has come to understand that both of them have the similar extent of symmetry with reference to the scale of level symmetry with different crystal structures as shown …show more content…
The structural evolution of this quartz type iron phosphate, FePO4 was observed using neutron powder diffraction from temperature varying from 294K-1073K. It also have a α-β phase transition at high temperature (980K).The refined structural parameters of the low temperature α phase tend towards the obtained values for high temperature β quartz type FePO4. The irregularities increase with the increasing temperature due to the excited low energy, high amplitude vibration in αquartz and resulted by the non-physical behaviours. The effect of this disorder is accommodated total neutron scattering measurement. In a tetrahedral distortion there is a change in both the angle and the length of the bonds which are present during the tetrahedral tilting. Only a change in the angle is resulted but no significance change in bon length. The increase in bridging angles between Fe—O—P and the tetrahedral angles greatly decrease as the α-β transition approach at high temperature at 980K. The tetrahedral tilt angle δ and the intertetrahedral bridging angle θ can be related to the degree of distortion with respect to β-quartz structure type. The α-β transition is not observed for most material under the condition that δ value is greater than 22 degrees and θ value less than 136 degrees. However, the structural parameters of FePO4

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