Paragraph 1
This paper talks about how the crystal structure of FePO4will change at different ranges of temperatures.
FePO4 has a crystal structure which is similar to quartz, which is made up of 2 phases at different temperatures. At low temperature, FePO4 will demonstrate α phase till the transition temperature of
980K before demonstrating the β phase. Space group of α phase FePO4 is said to be P3121, thus suggesting it has a trigonal structure. As for β phase FePO4, the space group will be P6422, which suggests it has a hexagonal structure. The main reason behind this change is that during the transition period from α phase to β phase at 980K, the tetrahedral structure will start to rotate leading to a tilt angle, δ, being formed. As for …show more content…
If you consider quartz, it is quite similar too with the positive charge from Si4+ which is 4+.
And thus with 2 Si atoms in it, total positive charges will be 8+. As you have noticed, if we replaced the 2
Si atoms with 1 Fe atom and 1 P atom, they will also be able to create bonds with the O atom without any notable changes in the structure. Furthermore, by heating up SiO2, it would demonstrate the α phase at low temperatures and the β phase at high temperatures. This is also similar to that experienced by FePO4. Moreover, α and β phases of SiO2 are observed to have the same space group as that of FePO4.
For both structures, it can be observed that with an increase in temperature, there will be an increase in cell volume as well as the cell parameters. Thus this suggests that both these variables are dependent on temperature which in fact will cause angular variances such as change in the tilt and bridging angles.
Paragraph 2
As stated before, the transition temperature is 980K. Before 980K, FePO4 will most likely adopt a trigonal structure. Once it passes the transitional temperature, the crystal structure will change to hexagonal. By viewing these α and β unit cells at [001], their difference can be observed. At 294K, the α unit cell …show more content…
As for PO4, the bond length between P-O decrease as temperature increases. However for FeO4, there is only a slight change in bond length during the phase transition period. As for bond angle In the case of bond angles, it is quite similar to FeO4 with the exception that bond angles in O1-P-O1 are below 110o and bond angles in O1-P-O2 are above 110o
. Tilting angle of the structure can be expressed by the Landau-type model:
The tilt angle, δ is taken to be the overall average tilt angle. This is due to tilt angles of FeO4 and PO4 being dependant on the fractional atomic coordinates of 2 oxygen atoms, O1 and O2 which are located in both structures. δ in both FeO4 and PO4 decreases as temperature increases, thus leading to overall average tilt angle to decrease. As for β phase, δ is found to be zero due to a limit on how much the structure can expand. As the structure fully expands, there will be no more thermal expansion, thus δ will also be zero according to the model above. At transition temperature, the cell parameters as well as fractional atomic numbers of the α phase are similar of those of the β phase. During the transition temperature, there is also a decrease in the bond length in the α
This paper talks about how the crystal structure of FePO4will change at different ranges of temperatures.
FePO4 has a crystal structure which is similar to quartz, which is made up of 2 phases at different temperatures. At low temperature, FePO4 will demonstrate α phase till the transition temperature of
980K before demonstrating the β phase. Space group of α phase FePO4 is said to be P3121, thus suggesting it has a trigonal structure. As for β phase FePO4, the space group will be P6422, which suggests it has a hexagonal structure. The main reason behind this change is that during the transition period from α phase to β phase at 980K, the tetrahedral structure will start to rotate leading to a tilt angle, δ, being formed. As for …show more content…
If you consider quartz, it is quite similar too with the positive charge from Si4+ which is 4+.
And thus with 2 Si atoms in it, total positive charges will be 8+. As you have noticed, if we replaced the 2
Si atoms with 1 Fe atom and 1 P atom, they will also be able to create bonds with the O atom without any notable changes in the structure. Furthermore, by heating up SiO2, it would demonstrate the α phase at low temperatures and the β phase at high temperatures. This is also similar to that experienced by FePO4. Moreover, α and β phases of SiO2 are observed to have the same space group as that of FePO4.
For both structures, it can be observed that with an increase in temperature, there will be an increase in cell volume as well as the cell parameters. Thus this suggests that both these variables are dependent on temperature which in fact will cause angular variances such as change in the tilt and bridging angles.
Paragraph 2
As stated before, the transition temperature is 980K. Before 980K, FePO4 will most likely adopt a trigonal structure. Once it passes the transitional temperature, the crystal structure will change to hexagonal. By viewing these α and β unit cells at [001], their difference can be observed. At 294K, the α unit cell …show more content…
As for PO4, the bond length between P-O decrease as temperature increases. However for FeO4, there is only a slight change in bond length during the phase transition period. As for bond angle In the case of bond angles, it is quite similar to FeO4 with the exception that bond angles in O1-P-O1 are below 110o and bond angles in O1-P-O2 are above 110o
. Tilting angle of the structure can be expressed by the Landau-type model:
The tilt angle, δ is taken to be the overall average tilt angle. This is due to tilt angles of FeO4 and PO4 being dependant on the fractional atomic coordinates of 2 oxygen atoms, O1 and O2 which are located in both structures. δ in both FeO4 and PO4 decreases as temperature increases, thus leading to overall average tilt angle to decrease. As for β phase, δ is found to be zero due to a limit on how much the structure can expand. As the structure fully expands, there will be no more thermal expansion, thus δ will also be zero according to the model above. At transition temperature, the cell parameters as well as fractional atomic numbers of the α phase are similar of those of the β phase. During the transition temperature, there is also a decrease in the bond length in the α