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..

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..

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 defects: Schottky defect Fre..

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..

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..

A negative ion may be missing from its lattice site, leaving a hole, which is occupied by an electron thereby maintaining an electrical balance. The trapped electrons are called F-centers or color centers because they are responsible for imparting color to the crystal. Example: NaCl when..

The contribution of electron to the conductivity is clearly negligible as compared to that of the holes. The conductivity of silicon doped with indium is much larger than its intrinsic conductivity (0.00044 S m - 1 ) The resistive is 0.0026 W m. It is very small as compared to the intrinsic resitivi..

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..