Synthesis, Structural and Luminescent Properties of Novel Eu3+:Y2CaZnO5 Nanophosphor for White Light-Emitting Diodes

Novel red-emitting phosphors, Eu3+-doped Y2CaZnO5 (YCZ), were synthesized by modified urea assisted sol-gel combustion method. The X-ray diffraction analysis indicates the uniform formation of single-phase triclinic YCZ nanoparticles even when the concentration of Eu3+ ions is as high as 50 mol%. TEM measurements revealed that the particles have uniform size distributions in the range of 10-30 nm. Luminescence properties have been characterized using photoluminescence excitation, emission spectra and decay time measurements. A strong charge transfer band (CTB) at around 250 nm is observed which is due to the Eu-O interaction in the host along with the 4f-4f excitation bands due to Eu3+ ions in UV and blue regions. The excitation bands at 395 nm (F-7(0) -> L-5(6)) and 465 nm (F-7(0) -> D-5(2)) are found to be stronger than the CTB for Eu3+:YCZ nanophosphor, which match very well with the emission wavelength of commercial InGaN blue LED chip. Upon excitation to these wavelengths, a bright red emission from the D-5(0) level of Eu3+ ion is observed with CIE chromaticity coordinates (0.65, 0.34), which are found to be very close to the National Television System Committee (NTSC) for red phosphor (0.67, 0.33).