ABSTRACT
Despite extensive research on the photoluminescence properties of Bi3+ ions, the origins of their emission and excitation bands remain elusive. Herein, we present a comprehensive analysis of the photoluminescence properties of Bi3+-activated LuXnGaO4 (Xn = Mg, Zn), elucidating the underlying factors governing the intra-ionic and extra-ionic electronic transitions. By integrating crystal structure data and spectroscopic data analyses with semi-empirical formula calculations, the origins of excitation and emission states were elucidated. Moreover, the impact of alterations in chemical surroundings on the luminescence of Bi3+ was investigated. Both LuXnGaO4:Bi3+ phosphors exhibit three excitation peaks in the near ultraviolet region and display a broadband yellow emission. However, the luminous behavior of LuMgGaO4:Bi3+ and LuZnGaO4:Bi3+ differs due to variations in the band gap, bond length and neighboring atoms. It is anticipated that the investigation of Bi3+-activated gallates presents a promising avenue for advancing wide-band and long-wavelength emitting phosphors.
ABSTRACT
In order to realize broad excitation and narrow emission red light phosphor, a new vanadium phosphate Ba2BiV2PO11 was selected as a host for Eu3+. Monitored at 619 nm, a wide band from 240 to 400 nm could be observed and inferred to be composed of Eu3+-O2- and V5+-O2- charge transfer bands, which could make it match well with the UV chip and the blue chip along with the characteristic excitation of Eu3+ at 465 nm. Under 354 nm excitation, the sample could emit high color purity red light, and the thermal quenching integral intensity showed good thermal stability. The generation of charge transfer bands was investigated in detail combined with the luminescence properties and the structure of the matrix. Moreover, the as-prepared phosphor could improve the white light performance of blue chip-activated YAG:Ce3+ and n-UV chip-activated tricolor phosphors. All the results indicated the multiple application potential of Ba2BiV2PO11:Eu3+ for white light-emitting diodes.
ABSTRACT
A novel apatite-based phosphor MgGd4Si3O13[Mg2Gd8(SiO4)6O2]:Ce3+, Mn2+ was designed and successfully synthesized by a solid-state reaction. Based on the different luminescence properties under 298 and 340 nm excitations, its potential application as a dual-excitation luminescent ratiometric thermometer was studied in detail. Under the excitations of 298 and 340 nm, the fluorescent intensity ratio of Ce3+ and Mn2+ is linearly correlated in the temperature range of 303-473 K. The sensitivity showed an opposite trend with the increase of temperature, and the maximum value was 0.95% K-1. These results indicated that MgGd4Si3O13: Ce3+, Mn2+ can be used as an ideal dual-excitation luminescent ratiometric thermometer.
ABSTRACT
Owing to the broad application scope of phosphors for light and display, the development of narrow-band light-emitting phosphors has recently gained considerable research attention. In this study, a new type of narrow-band blue light-emitting phosphor, Rb2HfSi3O9:Eu2+, with a full width at half maximum (FWHM) of 64 nm was synthesized successfully. Upon the near visible ultraviolet (NUV) light excitation, the internal quantum efficiency of Rb2HfSi3O9:Eu2+ was 68%. It also exhibited good thermal stability, which was higher than that of a commercial blue phosphor (BaMgAl10O17:Eu2+) at 150 °C. The significant photoluminescence properties of Rb2HfSi3O9:Eu2+ were found to be related to its robust crystal structure, which was investigated in detail. The results indicate that Eu2+-activated Rb2HfSi3O9 is a promising phosphor for use in white light-emitting diodes.
ABSTRACT
A series of novel red emission Mg3Ga2GeO8 (MGG):Mn(4+) phosphors under near-UV (NUV) excitation are synthesized successfully by traditional high-temperature solid-state reaction. The structure of Mg3Ga2GeO8 is investigated by high-resolution transmission electron microscopy, scanning electron microscopy, and powder X-ray diffraction (XRD) Rietveld refinement. It has one octahedral site and one tetrahedral site in the crystal structure. According to XRD and photoluminescence (PL) property analysis, Mn(4+) can occupy an octahedral (Mg(2+)/Ga(3+)) site. The PL properties are investigated by diffuse-reflectance, emission, excitation, and temperature-dependent spectroscopy and decay curves. It can emit red light peaking at 659 nm under NUV excitation. The critical quenching concentration of Mn(4+) was about 0.5 mol %. The concentration quenching mechanism could be a d-d interaction for the Mn(4+) center. The CIE chromaticity coordinates and full-width at half-maximum are (0.295, 0.677) and 24 nm, respectively. It demonstrated that MGG:Mn(4+) has high color purity. The PL intensity of MGG:0.5% Mn(4+) drops to 72% when the temperature is raised up to 150 °C. Furthermore, MGG:0.5% Mn(4+) exhibits outstanding quantum efficiency (64.7%). By tuning of the weight ratio of blue, green, and red phosphors, the fabricated white-light-emitting diodes using a 405 nm GaN NUV chip combined with a blend of blue phosphor BAM:Eu(2+), green phosphor Sr2SiO4:Eu(2+), and red-emitting phosphor MGG:Mn(4+) driven by 40 mA current can get white light with chromaticity coordinates (0.316, 0.375) and CCT = 3340 K. This demonstrates that MGG:Mn(4+) is a potential red phosphor matching NUV LED chips to get white light.
ABSTRACT
A novel phosphate RbZnPO4 has been developed for the first time and the characteristic crystal structure of RbZnPO4 has been investigated in detail, based on the Fourier transform infrared reflection spectra and the structure refinement of X-ray diffraction data. After doping with Eu(3+),RbZnPO4:Eu(3+) shows distinctive deep red emission with dominating peaks at 596 and 701 nm. To provide a reasonable explanation for the relationship between photoluminescence and structure, the photoluminescence property has been discussed by analyzing the particular local ligand environment and site occupation of Eu(3+) in RbZnPO4. More interestingly, temperature-sensitive emission behavior was found in RbZnPO4:Eu(3+). Through the synthetical analysis of the configurational coordinate diagram, the charge compensation experiment and the CASTEP band structure calculation, a complex underlying mechanism is proposed to explain the abnormal temperature-sensitive emission behavior in RbZnPO4:Eu(3+). The mechanism could be helpful for better understanding the thermal quenching process of Eu(3+) in RbZnPO4 and also as a reference in some other temperature-sensitive phosphors.
