ABSTRACT
Thermoelectric effects arise at a junction of two different metals. When two different metals are in contact, electrons cross the junction from one metal to other giving rise to electric field. This effect is known as Peltier effect. The Hall effect and dielectric materials have been described in this chapter. Piezoelectric, ferroelectric and antiferroelectric crystals have also been discussed. A crystal may behave as piezoelectric without being ferroelectric. Optical processes such as photoluminescence, fluorescence and phosphorescence have been explained in detail with the help of energy diagram. When alkali halides are doped with activators such as thallous ion (Tl+), luminescence is exhibited. Allowed transitions have also been explained. Dielectric materials are insulating materials used in capacitors and electrical insulators. Polarizability of dielectric materials has been incorporated in this chapter.
