Composition And Photoluminescence Of Novel Oxynitride Phosphors Synthesized At Low Temperature

White light-emitting diodes(WLEDs)have become one of the most promising light sources since the bright-blue LEDs emerged as a landmark achievement in solid-state lighting in the mid,1990s,and created quite a stir when the Nobel Prize in Physics was awarded jointly to Isamu Akasaki et al.for the invention of efficient blue LEDs which has enabled bright and energy-saving white light sources.Phosphors applied as down-conversion luminescent materials play a vital role in determining optical properties of WLEDs.They have a broad range of material systems,of which(oxy)nitride phosphors are the most promising candidate for WLEDs due to the outstanding advantages including high thermal and chemical stability,small thermal quenching and enhanced luminescence properties.Remarkable and efficient as they are,the drawbacks including strict synthetic conditions,complex procedures and high costs should not be neglected.Therefore,developing an inexpensive,straightforward,and efficient method to synthesize(oxy)nitride phosphors is in great demand from the view point of industrial applications.Based on this point,the low-temperature synthesis of(oxy)nitride phosphors at room pressure(RP),as well as their photoluminescent(PL)properties,have been fully researched in this work.In Chapter 3,the nitridation reacted at low tempertature(RP)has been studied,and a new method to synthesize(oxy)nitride phosphors has been proposed.The results indicate that using rare earth(RE)ions doped Ca3(PO4)2 as precursor is an efficient method to obtaion(oxy)nitride phosphors.In Chapter 4,CaSi2O2N2:Tb3+-Ce3+phosphors have been successfully synthesized by Ca3(PO4)2 precursor method at 1400?.This work confirms that sintering in N2/H2 atmosphere is better than in pure N2 for obtaining phosphors with higher PL intensity.The energy transfer(ET)of Ce3+?Tb3+in the CaSi2O2N2 host has been demonstrated to be resonant type via a dipole-dipole interaction mechanism.The corresponding emitting colors of CaSi2O2N2:Tb3+-Ce3+phosphors can be tuned between blue and green region under UV excitation.In Chapter 5,the photoluminescent properties of Ca2Si3O2N4:Yb2+-Dy3+phosphors synthesized by Ca3(PO4)2 precursor method have been systematically investigated.In Chapter 6,a new method in which CaCN2 is applied as calcium provider has been reported.The photoluminescent properties of Ca2AlSi3O2N5:Eu2+/Mn2+has been studied.It is interesting to note that there are two different kinds of Ca2+sites in the Ca2AlSi3O2N5 host according to the PL spectra.