Engineering Chemistry S Datta

SILICATE TECHNOLOGY 417
Clay or silicates are common raw materials for
• Ceramic industries
• Refractory industries
• Glass industries and
• Cement industries.
For that reason the technologies of these industries fall under the common name silicate
technology. Generally silicate materials are bad conductor of heat and electricity. Now-a-days,
some new types of ceramics are discovered with electrical and magnetic properties. These
properties depend on their unit structure. These ceramics are called high performance ceramics.
The individual solid metal oxides were mixed in the proper ratio, ground well and finally
heated to 1000°C for 12 hrs, at this high temperature the individual oxides are converted into
the mixed oxide compound. The property of super-conductivity in these compounds is dependent
on a particular characteristic of arrangements of constituent atoms. For example, in YBa 2
Cu 3
O 7–y
(see Fig. 19.5) successive horizontal layers of copper-oxygen sheets are separated by ribbonlike
chains of copper-oxygen. The square copper-oxygen sheets are the pathways of superconducting
electrons in these compounds. Even slight alteration of the arrangement of atoms
destroys superconductivity. The preparation of superconducting ceramic therefore, is an
exacting piece of work.
Oxygen
Copper
Ba
Ba
Y
Y
Ba
Ba
Ba
Ba
Y
Y
Ba
Ba
Fig. 19.5 The crystal lattice of YBa 2
Cu 3
O 7–y
.