Temperature Lab Report

923 Words 4 Pages
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WRITTEN ESSAY
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The FePO4 crystal is examined at various temperatures ranging between 294K and 1073K by neutron powder diffraction. At relatively low temperatures, FePO4 adopts an α-quartz structure, which is tetrahedral. High pressures causes a phase change to a more dense octahedral structure, which is known as β-phase.
The transition temperature is 980K. Cutoffs can be observed during the firstorder transition,. For α-phase, the increases in cell parameters with respect to increase in temperature show a non-linear trend. The thermal expansion coefficient a is expressed as α (K-1)= 2.924 x 10-5 + 2.920 x 10-10 (T-300)2.
The major components contributing towards this are the variations in the Fe-O-P
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The cell parameter rises significantly with the temperature, which subsequently leads to a rise in volume. With an increase in temperature, the bent Fe-O-P bond expands and increases notably due to the process of preferential expansion.
At the transition temperature (980K), The structural parameters of the lowtemperature α phase and high-temperature β-quartzFePO4 tend to be similar.
FePO4. Hence we can conclude that it changes from the α to β phase. There is no substantial change in the bond distance or the angle in the β phase.
When the temperature is almost close to the phase transition temperature, it can also be observed that the tilt angle decreases notably.
The ATOMS drawings are shown to supplement the above observations.
Cell parameters as a function of temperature (Haines et. All)
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Cell volume as a function of temperature. (Haines et. All)
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We already know that the structural parameters for low-temperature α phase and high-temperature β-quartzFePO4 tend to be similar. It is believed that both the tilt angle and the bridging angle may be potential causes to

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