(Oxy)Nitride Phosphors For Solid State Lighting

Solid state lightings have attracted much attention and have been considered as a new generation of the lighting source. In comparation to the traditional incandescence lamp and fluorescence lamp, solid state lightings possess excellent properties, such as a high efficiency, long lifetime, environmental friendship, extensive applications, and so on. Among them, white LED gains a great interest for the general illumination source and has been widely used in our life. At present, the dominant commercialized approach to achieve white LED is by combining a blue LED chip with a yellow-emitting Y3Al5O12:Ce3+phosphor. Although the fabricated white LEDs exhibt a high luminous efficacy, the color rendering index is low (Ra<75) and the correlated color temperature is high (CCT>5000K). This is caused by lack of the red component in the emission spectrum of the YAG:Ce3+phosphor. Therefore, in order to improve the performance of white LED, it is necessary to adjust the emission spectrum of Y3Al5O12:Ce3+.Recently, researchers propose a new concept of solid state lighting, termed as field emitting lamp (FEL). It exhibits a great potential in the lighting, because of the uniform light output, a simple structure, and the low cost. To the best of our knowledge, researches play much attention on cathode materials, however, optical properties of white FEL are not systematically investigated yet. Especially, there are no reports on fabricating white FEL by using oxynitride/nitride phosphors.Focusing on the above problems, this thesis carried out following researches:(1)Y2.925Ce0.075Al5-xSixO12-xNx phosphors were successfully synthesized by a simple gas pressure sinteing method. The effect of Si4+-N3-incorporation on optical properties of the Y3Al5O12:Ce3+phosphor was investigated in detail. The addition of Si3N4leads to an obvious shift of emission spectra toward the red light region and an increase of FWHM accompanying a significant decrease of the photoluminescent intensity. Adding nanosized Si3N4or flux can greatly improve the emission intensity of the Y2.925Ce0.075Al5-xSixO12-xNx phosphor. Finally, the white LED flat lamp with a CRI as high as83, a luminous efficiency of65lm/W, and a CCT of about3700K is successfully realized by using a single oxynitride phosphor combined with a blue LED chip, which is acceptable for general indoor illuminations.(2) Y3Al5-xBxO12-xNx:Ce3+phosphor was synthesized by a simple gas pressure sintering method. The effect of B3+-N3-incorporation on optical properties of the Y3Al5O12:Ce3+phosphor was investigated in detail. The addition of appropriate amounts of boron nitride (BN) leads to a marked increment in the photoluminescent intensity. Finally, the white LED flat lamp with a luminous efficiency as high as101lm/W, color rendering index of72, and a correlated color temperature of about6600K is successfully realized by using the prepared oxynitride phosphor.(3) Eu2+-doped AIN-polytypoids (8H,15R,12H, and21R) were successfully synthesized by the nitrogen-gas-pressure sintering method. The phosphors show intense blue emissions under the UV light or electron beam excitation. All the polytypoid phosphors exhibit a high thermal stability, and a low voltage and electric saturation.(4) Mn2+doped-AIN red phosphor was prepared by the gas pressure sintering method in the nitrogen atmosphere. Under the UV light or electron beam excitation, the AlN:Mn2+phosphor exhibits a strong red emission centered at600nm. The oxygen-related defects in AlN have great influences in luminescence properties of the AlN:Mn2+phosphor. The dependence of brightness on the accelerating voltage or electric current, and the decay behavior of CL intensity under the electron bombardment were investigated in detail. The results indicate that the AlN:Mn2+phosphor exhibits a high brightness, low saturation, and high stability compared to the red Y2O3:Eu3+phosphor.(5) White field emission lamp (FEL) was achieved by using blue AlN:Eu2+, and yellow Ca-a-SiAlON:Eu2+phosphors, or by using blue AlN:Eu2+, green β-SiAlON:Eu2+, and red CaAlSiN3:Eu2+phosphors. Compared to white LED fabricated by the above phosphors, white FEL exhibits an uniform light output, and a tunable color rendering index or color temperature. Especially, the color rendering index of white FEL, realized by using three types of phosphors, achieves97. The results indicate that white FEL might be a potential solid state lighting source.