Piezoelectric effect was first observed by Curie brothers in the year 1980. Photoelectric effect is the phenomenon of development of charges in a crystal when mechanical force or tension is applied on it. A voltage can be developed in such crystals by suitable mechanical deformation. Quartz is an example of dielectric material. Quartz is silicon dioxide and in its crystal, atoms are arranged to form a hexagon in one plane with optic axis perpendicular to this plane. Some other examples of naturally occurring piezoelectric materials are Rochelle salt and tourmaline. Some examples of artificially synthesized piezoelectric materials are ammonium dihydrogen phosphate, Lithium sulphate and Dipotassium tartarate. Quartz is stable, unaffected by humidity and has no useful shear mode. Artificially grown quartz is preferred than the natural quartz for piezoelectric applications. Tourmaline is used in applications where a large sensitivity in the volume expander mode is required. For the production of gramophone pick-ups and crystal microphones, Rochelle salt is used which carries high relative permittivity and is very much temperature sensitive. Ammonium dihydrogen phosphate crystals are temperature dependent and possess low values of resistivity.
No comments:
Post a Comment