RESUMO
Here, the crystal structure, phase analysis, site occupancy, and luminescence properties of NCMP:Eu2+,Tb3+,Mn2+ have been studied for the first time. Under 335 nm ultraviolet excitation, the NCMP:Eu2+ phosphors show narrow-band blue emission. In addition, we discuss the reason for a continuous red shift for the emission spectra of NCMP:xEu2+ by raising the x value. The efficient ET processes of Eu2+ â Tb3+ and Eu2+ â Mn2+ were investigated by the luminescence spectra and decay curves. The ET efficiencies reach 92.58% at y = 0.15 for NCMP:0.01Eu2+,yTb3+ and 99.85% at z = 0.15 for NCMP:0.01Eu2+,zMn2+ phosphors, respectively. The efficient energy transfer processes greatly improve the quantum efficiency, luminous intensity, and thermal stability. Bright green and red emissions can be realized through changing the related ratio of Eu2+, Tb3+, and Mn2+. In addition, the excellent performance of the prepared white LED lamps utilizing a 385 nm chip combined with our prepared NCMP:Eu2+,Tb3+/Mn2+ phosphors indicates that NCMP:0.01Eu2+,yTb3+ and NCMP:0.01Eu2+,zMn2+ phosphors can be potential green and red phosphors for white LEDs.
RESUMO
Structure determines properties, and properties determine applications, which is an important ideology of natural sciences. For optical materials, it is vital to lucubrate the corresponding relationship between the local crystal structure and luminescence properties for their design, synthesis, and application. This work reports a newly designed Y2Mg2Al2Si2O12(YMAS):Eu3+ red phosphor, in which difunctional Eu3+ ion is used as a red-light activator and spectroscopic probe. The qualitative and quantitative studies on the relationship between the local crystal structure and the luminescence properties of YMAS:Eu3+ are performed experimentally and computationally, using the Y3Al5O12 (YAG):Eu3+ as contrast. Moreover, compared with YAG:Eu3+, the newly designed YMAS:Eu3+ has stronger luminescence, superior Commission Internationale de L'Eclairage chromaticity coordinates, a lower optimal doping concentration, and equally excellent thermal stability. The satisfactory color-rendering index of packaged white-light-emitting diodes demonstrates its potential performance as a red phosphor. Briefly, this work provides not only a new case for the study of the local crystal structure and luminescence properties but also a new possibility for the application of a red phosphor in solid-state lighting.
RESUMO
A modified structure Ca(Mg0.8Al0.2)(Si1.8Al0.2)O6 (denoted as CMASO) from the evolution of CaMgSi2O6 (denoted as CMSO) codoped with Ce3+ and Tb3+ ions was designed successfully by solid reaction method for application in phosphor-converted white-light-emitting diode (pc-wLED). The Rietveld refinement of these two structures verified the changes derived from the replacement of some of the Mg2+ and Si4+ ions by Al3+ ions. The band gaps were calculated by density-functional theory (DFT) calculation method to verify the change of Al3+ ions replacing further, and the diffuse reflectance spectra (DRS) proved the veracity of the calculation result. The phosphors CMASO:Ce3+ showed blue emission excited by a wider excitation wavelength from 280 nm to 370 nm. The change of structure lead to the absorbable range broaden and the emission peak shifted to longer wavelength, compared with CMSO:Ce3+, although the amount of emitting center was the same. The reason for these phenomena was discussed in detail. The codoped phosphors CMASO:Ce3+,Tb3+ exhibited different emission colors from blue to green as the concentration of Tb3+ ions increased. Combined with commercial red phosphor CaAlSiN3:Eu2+ and ultraviolet LED (UV-LED) chips, the selected appropriate samples achieved white emission. The correlated color temperature (CCT) was 6137 K and the color rendering index (Ra) was 80.5, indicating that they could act as potential phosphors for possible applications in pc-wLED.