Α-Fepo4 Lab Report

1.Compare and contrast the crystal structures and crystal chemistry of quartz α-FePO4 and β-FePO4
FePO4 is an extremely distinct quartz as its cation is a transition metal. It is often looked in depth at temperatures ranging from 294K to 1073K. When it is at a relatively low temperature, we see the quartz at α-FePO4. It takes on a tetrahedral shape. At higher temperatures, the α-FePO4 will transition to β-FePO4 and takes on an octahedral shape. Very importantly, the temperature at which this transition occurs is at 980K. When temperatures are below 980K, the quartz takes the form of α-FePO4 and at 980K, starts to transition to β-FePO4. During the α-phase of FePO4, the cell parameters increased in a non-linear fashion against temperature. This
The α- β transition is highly dependent on two factors. Firstly, it is dependent on the tilt angle δ. Secondly, it is also dependent on the angular variations caused by changes in the inter-tetrahedral FePO4. The overall average tilt angle that we use in calculations is taken as the individual average of the tilt angles. Interestingly, the behavior is not the same as other α-quartz homeotypes. The δ angle begins to decrease in a more rapid fashion than quartz. Volumetric dependence on temperature is ruled by the behaviour of the average δ and θ angles as a function of temperature.

2.Illustrate and describe the symmetrical differences between α-FePO4 and β-FePO4.

Figure 1: The Unit Cell
At 980K, FePO4 will transition from α-FePO4 (at a temperature below 980K) to β-FePO4 (at a temperature above 980K). When α- β transition occurs, unit cell structure symmetry transitions from trigonal to hexagonal. While the symmetry of α-FePO4 is trigonal, the
The quartz type, iron phosphate, during structural evolution, was observed using neutron powder diffraction from temperature varying from 294K-1073K. The parameters of the α phase when it at relatively low temperatures moves towards values indicated by relatively high temperature β quartz type FePO4. Quartz exhibits a α-β phase transition at high temperature (980K). The tetrahedral tiling is of high importance as it determines the distinct structural property and identity. The tetrahedral tilt angle δ, in addition with inter tetrahedral bridging angle θ, is said to constitute the tetrahedral distortion. The change in the bond length as well as the cell angle, when temperature rise, also contributes to the tetrahedral distortion. To summarise, tetrahedral distortion is the product of tetrahedral tilting, which can be quantified by tilt angle δ and is significantly temperature dependent. When the δ value is greater than 22 and θ value less than 136 degrees, for most materials, the α-β transition is not observed. However, the structural parameters of FePO4 (δ=21.5and θ= 137.8) are very near to the above limiting values. It is observed that, at high temperatures of about four hours, the result is that FeO4 the bond length and tetrahedral bond angles in quartz type FePO is a function of temperature. When temperatures increase from 294K to 969K, it is observed that FeO2 decreases in length and hence,