Introduction to Borate Phosphors

Abstract

The need of new materials with desirable optical properties has become important in recent years. In particular, a need has emerged for compounds having better luminescent properties in various practical applications. Introduction of rare earth ions as activators improves the luminescence properties of the compounds considerably. Borates form a great number of compounds having diverse structures due to three-fold or four-fold coordination of borate atoms. Borates intrinsically possess characteristics that are advantageous for optical materials, which include wide transparency range, large electronic band gap, good thermal and chemical stability, low preparative temperature, optical stability with good nonlinear characteristics and exceptionally high optical damage threshold. The unique crystal structure of borates determines their enhanced UV transparency, good nonlinearity and relatively high resistance against laser induced damage. Recent research on inorganic borates has been focused on the synthesis and characterization of compounds with potential application as optical material. Borate compounds currently have been of considerable interest to the scientific community due to their wide range of applications: laser, NLO material, phosphor material and scintillator material, etc. Most of the borates are polyfunctional materials with nonlinear optical, piezo-electrical and acousto-electrical properties. Some borates are also suitable as a laser material for miniature laser. Variety of borate host materials doped with rare earth and other ions have been reported as phosphor materials for variety of applications. This chapter gives a brief introduction to classification of luminescence, their phenomenological theories and applications in various fields. It also deals with the borates, classification of borate compounds on the basis of chemical formula and crystal structure, crystal chemistry of borates and applications in various fields.