1. Crystal Structure and Crystallography of Materials
Chapter 4: Silicate Structure

2. Silicate Ceramics: Silicates: Basic building block SiO4-4 tetrahedron
bond length Si-O 1.62 Å
SiO4-4
tetrahedron

3. Quartz (SiO2): Crystalline form of SiO2
Z=3 (No. of formula units per cell)

4. TRANSFORMATION
displace
reconstruct

5. Allotropic Forms of Quartz (SIO2)

6. Polymorphic Forms of Quartz (SIO2)
SiO2 (Quartz P3221 (154) [hP9]) Si at ,0,2/3 O at ,0.2662,0.7855
Trigonal

7. Polymorphic Forms of Quartz (SIO2)
SiO2 ,(Cristobalite - high Fd-3m (227) [cF24]) Si at 0,0,0 O at 1/8,1/8,1/8
FCC

8. Polymorphic Forms of Quartz (SIO2)
SiO2 (Tridymite)
P63/mmc (194) [hP12] Si at 1/3,2/3, O1 at 1/3,2/3,1/4 O2 at 1/2,0,1/2
Hexagonal

9. SILICA GLASS network former network modifier: Na2O, CaO
noncrystalline, fused silica, vitreous silica
network former
network modifier: Na2O, CaO
intermediate: Al2O3, TiO2

10. SILICATES
Sharing of oxygen ions in
tetrahedra

11. SILICATES
Independent tetrahedra (nesosilicate): 1:4 ratio of Si: O
ex) Mg2SiO4 (forsterite, olivine), ZrSiO4 (zircon)
olivine

12. SILICATES Pair of tetrahedra: 2:7 ratio of Si:O (sorosilicate)
ex) Zn4Si2O7(OH)2H2O (hemimorphite), Sc2Si2O7 (thorvetite)
hemimorphite

13. SILICATES ring silicate: 1:3 ratio of Si: O (cyclosilicate)
ex) BaTiSi3O9 (benitoit), Be3Al2Si6O18 (beryl)
green, emerald
benitoit

14. SILICATES chain silicate: 1:3 ratio of Si: O (inosilicate) pyroxene
ex) MgCaSi2O6 (diopside), LiAl(SiO3)2 (spodumene),
Ca2Mg5Si4O11(OH)2 (tremolite)
pyroxene
amphibole

15. SILICATES Layer silicates- Kaolinite (Al2(Si2O5)(OH)4)
(Si2O5)2- layer + Al2(OH)42+ layer