Contrast The Crystal Chemistry Of Quartz, Fepo4, Α-Fepo4?

Paragraph 1 - Compare and contrast the crystal structures and crystal chemistry of quartz, α-FePO4 and β-FePO4.
Both α-FePO4 (space group: P3121) and α-quartz (space group: P3121 and P3221) belong to the trigonal crystal system, while β- FePO4 (space group: P6422) and β-quartz (space group: P6222 and P6422) belong to the hexagonal crystal system. At relatively low temperature, FePO4 is tetrahedral in structure. This is similar to the tetrahedral structure of quartz. As temperature increases, the tetrahedral structure gradually transforms to a octahedral structure, known as the β-phase of FePO4.
Despite the differences in crystal chemistry of FePO4and quartz, they were still able to maintain a similar crystal system and tetrahedral structure. In quartz, the Silicon ion is tetravalent. In FePO4, the Iron ion is trivalent while the Phosphorus ion is pentavalent. Thus, the Iron ion and Phosphorus ion can replace 2 Silicon ions, which allows for the maintenance of a similar crystal system and tetrahedral structure. The following equation illustrates the replacement:
When either of them are exposed to high temperature, the α-β phase change will occur. The transition temperature lies at 980K for FePO4and 846K for