Iron Phostate Lab Report

Iron phostate, also extensively known as FePO4, was studied through a special type of transformation process known as neutron powder diffraction. The transformation process uses a temperature that ranges from 297K to 1073K. As long as it is within the low temperature range, it is defined as the ‘α’ phase. Otherwise, if it is within the high temperature range, it is defined as the ‘β’ phase. The iron phostate will change its tetrahedral form in the low temperature range to its octahedral form in high temperature range. However, in the first-order phase transition, it can be seen that the structural changes was discontinued, this is defined by a temperature that is near 980K. As the temperature continues to increase, the cell parameters and volume tends to increase in a

As such, in the low temperature of α phase, the structural properties will incline towards the values observed for high temperature in β phase of FePO4.

As the temperature increases, the tetrahedral form is being distorted by vibrations where the cell parameters and volume of α phase increases in a non-linear manner, it causes the change in angle and length of bond of the FePO4 structure. As the α-β phase transition reaches the temperature of 980K, the tetrahedral angle decreases and the FE-O-P bridging angles increases.

The main influence to the thermal expansion of FePO4 is known as angular variation where there is change between the two symmetrically-independent intertetrahedral bridging angles and its tilt angles. Thus, in relevance to temperature dependence on thermal expansion, the temperature is indirectly dependent on the angular variations of its bridging angles and tilt angles. Using the Landau-type model formula, δ

2 = 2/3 δ0

2

[1 + (1 – ¾ (T – Tc/T0 – Tc))^1/2], where at T0 =980K, δ0 is the drop in tilt angle and Tc is the temperature of second order transition, the dependence on the angle can be derived. Above that, during the occurrence