volume defects in crystals

Defects in Crystals - According to third law of thermodynamic it is only at OK that true crystals passes perfect order of arrangement of atoms in pure crystals. But with rise in temperature some derivations from complete order takes place. Presence of impurit..

According to third law of thermodynamic it is only at OK that true crystals passes perfect order of arrangement of atoms in pure crystals. But with rise in temperature some derivations from complete order takes place. Presence of impurities also adds to disorde..

The defect, which arises due to the irregularity in the arrangement of atoms or ions are called point defects..

As the number of ions decrease, volume is the same, so density decreases. Crystals with Schottky defect conduct electricity to a small extent. Due to the presence of holes the stability of the crystal decreases..

Stoichiometric Defects - If imperfections in the crystal are such that the ratio between the anions and cations remain same as represented by the molecular formula, the defect is called a stoichiometric defect. There are three types of stoichiometric def..

In in ionic crystal of the type A + B - , equal number of anions and cations are missing from the lattice sites so that electrical neutrality is maintained it is called schottky defect. fig 2.29 - Schottky defect..

In case of ionic solids, the impurities are introduced by adding impurity of ions. If the impurity ions are in a different oxidation state from that of the host ions, vacancies are created. For e.g., If molten NaCl, containing a little of SrCl 2 as impurity is allowed to cool, in the crystal..

Solids with this defect conduct electricity to a small extent The dielectric constant of the crystal increases The density of the solid is unchanged Due to the presence of holes, the stability of the crystal decreases..

X-Rays follow a rectilinear propagation and travel with a velocity of 3 x 10 8 ms - 1 in vacuum. They are not deflected by electric and magnetic field. Since they do not contain any charge but are diffracted by crystals, X-rays cause fluorescence when incident on certain materials such..

It is a white powder When mixed with water, it forms a plastic mass. After about half an hour, this mass sets into a hard solid mass constituting interlaced gypsum crystals. The volume slightly expands (about-1%) during setting. Because of this it is used in making cast..