Luminiscenční vlastnosti ternárních nitridů křemíku dopovaných lanthanoidy

Abstract

Since the end of last century the electric lighting consumes more and more energy, recently about 20 % of total electric energy consumption. For that reason the non-efficient incandescent and fluorescent lamps are replaced by white light emitting diodes (LED) which represent the next generation of light sources. Recently ceramic materials based on ternary nitrides are intensively studied mainly due to their good mechanical properties, chemical and thermal stability, and especially ability to serve as a host lattice for the phosphors. The main objective of this Ph.D. thesis is the preparation of ternary silicon nitrides doped with different rare earth elements (Eu, Ce and Sm) and the evaluation of their luminescence properties. By the optimization of the nitridation conditions and high-temperature annealing of metal silicide, silicon, silicon nitride and rare earth oxide efficient MgSiN2 and LaSi3N5-based phosphors were prepared. The photoluminescence measurements showed that by appropriate combination of host lattice (MgSiN2 or LaSi3N5) and rare earth dopant (Eu, Ce, Sm) (oxy)nitride-based phosphors can be prepared, which cover the whole visible light region: LaSi3N5:Ce phosphor – violet-blue light, MgSiN2:Ce – blue-green, LaSi3N5:Eu – green-yellow, MgSiN2:Eu – red and LaSi3N5:Sm – red light. By the combination of these phosphors white LEDs can be prepared. Moreover, the high intensity red and green phosphors allow the construction of highly efficient "warm" white LED with a yellowish daylight tinge. These LEDs can be widely used for indoor lighting and significantly contribute to energy saving.