ABSTRACT
The quenching free photoluminescence in fully concentrated rare-earth-based optical materials makes them excellent candidates for various optoelectronic applications. The factors leading to quenching free luminescence is the focal theme of this chapter. It covers the basic description of different quenching processes like concentration quenching, cross-relaxation quenching, phonon-assisted quenching, and hydroxyl quenching in luminescent materials. This chapter also describes the photoluminescence properties of fully concentrated rare-earth oxalate with terbium oxalate as a representative case. The crystal structure of rare-earth oxalate facilitates well-separated luminescence centers and there is least possibility for energy migration between identical luminescent centers thus weakening concentration quenching in this matrix. The quenching free nature of terbium oxalate is analyzed further by studying the variation of photoluminescence emission with the concentration of Tb3+ incorporated in lanthanum oxalate matrix up to the full concentration of terbium.
