The color point tuning
is significant for expanding the application
of optical materials (phosphors). In this work, one type of single
Eu2+-activated high bright phosphor was prepared, and the
color point could be tuned only by controlling the doping level of
the activator ion. The phase and crystal structure of the matrix material
Y2Mg2Al2Si2O12 (YMAS) were identified and analyzed. The luminescence properties
including excitation and emission spectra, peak position attribution,
spectral tuning, variation of luminescent intensity, and full width
at half-maximum were investigated and explained. The application performance
of phosphors and light-emitting diode (LED) devices were tested and
discussed. All above results reveal that the YMAS:Eu2+ phosphors
can be considered as feasible candidates for ultraviolet LED applications
for solid state lighting and backlight display areas.
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.
A novel luminescence material of
emitting color-tunable Ca20Al26Mg3Si3O68 (denoted as CAMSO):Ce3+,Tb3+ phosphors have
been synthesized via the high temperature solid-phase reaction process.
The crystal cell structure, photoluminescence properties and application
performance such as thermal stability and LED device performance of
the phosphors were researched in detail. CAMSO:Ce3+,Tb3+ phosphors showed multicolor with the different concentration
of Ce3+ and Tb3+ ions. Although the concentration
of Ce3+ ions was settled and there was the existence of
energy transfer from Ce3+ to Tb3+ ions, it was
found that Ce3+ ions’ blue light emission intensity
showed abnormal increasing with the increase of Tb3+ ions
doping concentration. The irregular phenomenon was discussed in detail.
The phosphor CAMSO:0.2Ce3+,0.1Tb3+ photoluminescence
emission intensity motivated by 374 nm at 150 °C retained about
81% of that measured at room temperature, which demonstrating the
good thermal and color stability of the sample. In addition, the white
LED lamps were fabricated through mixing the sample CAMSO:0.2Ce3+,0.2Tb3+ and the commercial phosphor CaAlSiN3:Eu2+ and their performance has been measured.
The results show that this series of phosphors could be excellent
candidates for the application of UV-excited w-LEDs.
Excellent color-tunable Eu2+,Eu3+ co-doped Ca20Al26Mg3Si3O68 materials have been prepared and their structure related luminescence properties have been studied. Combined with electroluminescent chip, Ca20Al26Mg3Si3O68:Eu2+,Eu3+ shows multicolour emission.
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+ → Tb3+ and Eu2+ →
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.
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.
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