GLASSY ELECTROLYTE_1

DEFINITION
Glass is a rigid disorder network of liquid phase which is cooled to below freezing temperature. The liquid becomes a disorder network due to the complex molecular configuration or slow molecular transport. Therefor, Glass is an amorphous (non crystalline) solid material, which is typically brittle and optically transparent. Figure 1 shows the images of natural glass and the oldest glass made by mouth blown.

Figure 1. Images of Meldavite and the oldest mouth blown window glass (Source: wikipedia)

The structural rearrangement of most metal and molten salt can occur relatively easily due to these materials have high fluidity at  temperature above the freezing temperature. Meanwhile, many inorganis silicates have very low fluidity at above freezing temperature, therefor these inorganic silicates form glasses upon cooling process. This glass formation is related to the high silicon-oxygen single bond energies and the directional bonding requirements imposed by sp3 hybridization of silicon, as shown by Figure 2. During glass formation, the volume may change associated with heating and cooling. The curve of volume change is described in Figure 3.

Figure 2. sp3 hybridization of silica network

Figure 3. Volume change curve as the function of temperature

The glass transition, Tg, is the temperature at which a supercooled liquid becomes a glass.
The production process of glasses is listed below:
1. The melting of quartz sand, quartz sand is the main raw material of glass, as it described in Figure 4.
2. The shaping of glass while in viscous state
3. the control cooling of the shaped article

Figure 4. The quartz sand, the main raw material of glass (source: wikipedia)

There are three basic constituents present in ionically conducting glasses, e.g:

1. network former

2. network modifier

3. ionic salts

Network formers are compounds of a covalent nature such as SiO2, P2O5, GeS2 etc. They form macromolecular chains which are strongly cross-linked by an assembly consisting of tetrahedra (SiO4, PO4, BO4...) or triangle (BO3)which combine to form macro molecular chains by sharing corners or edges (Bruce, 1995).

Network modifiers include oxides or sulphides (e.g. Ag2O, Li2O, Ag2S, etc) which interact strongly with the structure of network formers. A chemical reaction leading to the breaking of the oxygen or sulphur bridge linking two network former cations with reaction as listed in equation (1) and (2)

          (1)

    (2)(Kawamura et al., 2006)


The scheme of primary network formers and network modifier are described in Figure 5.

Figure 5. Scheme of primary network former and network modifier

The mixing of network formers and modifiers often result in the enhancement of ionic conductivity and is called as mixed anion effect or mixed former effect. “It is mainly due to the change in the binding energy between the oxide and mobile cations caused by the network structure modifications”

Other example of network modifier reaction is listed in equation (3)

  (3)


see my publications in these links:
paper 1
paper 2
paper 3
paper 4 (it is free now)
book 1