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The Sm 3+ ion singly doped LiCa 3 ZnV 3 O 12 (LCZV) phosphors were synthesized by a traditional high-temperature solid-state method. The luminescence characteristics of the as-prepared samples were studied by photoluminescence excitation and emission spectra. Under 343 nm excitation, the synthesized phosphors exhibited color controllable emission induced by the efficient energy transfer from VO 4 3- groups to Sm 3+ ions. Besides, the energy transfer efficiency was revealed to be about 58.4% when the dopant concentration was 4 mol%. By utilizing the as-prepared LCZV:Sm 3+ phosphors, commercial BaMgAl 10 O 7 :Eu 2+ blue-emitting phosphors and a near-ultraviolet light-emitting diode (LED) chip, a white LED device was fabricated. Under an injection current of 100 mA, the packaged LED device emitted pure white light with high color rendering index (88.4) and proper correlated color temperature (4320 K). By analyzing the thermal quenching behavior of the VO 4 3- groups and Sm 3+ ions, the optical thermometric behavior of the Sm 3+ -doped LCZV compounds was investigated. The maximum absolute sensor sensitivity and relative sensor sensitivity were found to be 0.25 K -1 and 1.8% K -1 , respectively. Additionally, the emitting color of the studied samples was dependent on the temperature. Ultimately, the Sm 3+ -doped LCZV phosphors were potential candidates for indoor illumination, optical thermometry and safety signals in high temperature environments., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Far-red emitting phosphors LaScO 3 :Mn 4+ were successfully synthesized via a high-temperature solid-state reaction method. The X-ray powder diffraction confirmed that the pure-phase LaScO 3 :Mn 4+ phosphors had formed. Under 398 nm excitation, the LaScO 3 :Mn 4+ phosphors emitted far red light within the range of 650-800 nm peaking at 703 nm (14 225 cm -1 ) due to the 2 E g → 4 A 2g transition, which was close to the spectral absorption center of phytochrome P FR located at around 730 nm. The optimal doping concentration and luminescence concentration quenching mechanism of LaScO 3 :Mn 4+ phosphors was found to be 0.001 and electric dipole-dipole interaction, respectively. And the CIE chromaticity coordinates of the LaScO 3 :0.001Mn 4+ phosphor were (0.7324, 0.2676). The decay lifetimes of the LaScO 3 :Mn 4+ phosphors gradually decreased from 0.149 to 0.126 ms when the Mn 4+ doping concentration increased from 0.05 to 0.9 mol%. Crystal field analysis showed that the Mn 4+ ions experienced a strong crystal field in the LaScO 3 host. The research conducted on the LaScO 3 :Mn 4+ phosphors illustrated their potential application in plant lighting to control or regulate plant growth., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Single phase Eu 3+ -activated Ba 3 Y 4 O 9 (Ba 3 (Y 1- x Eu x ) 4 O 9 ) red-emitting phosphors with different Eu 3+ doping concentrations were synthesized by a high temperature solid-state reaction method. The phase purity, crystal structure, photoluminescence properties, internal quantum efficiency, decay lifetimes, and thermal stability were investigated. Upon excitation at 396 nm near-ultraviolet light and 469 nm blue light, the Ba 3 (Y 1- x Eu x ) 4 O 9 phosphors exhibited a strong red emission at 614 nm due to the 5 D 0 → 7 F 2 transition of Eu 3+ ions. The optimal doping concentration of Eu 3+ ions in Ba 3 (Y 1- x Eu x ) 4 O 9 was found to be x = 0.25. Furthermore, the critical distance was calculated to be 12.78 Å and the energy transfer mechanism for the concentration quenching effect was determined to be quadrupole-quadrupole interaction. In addition, the Commission Internationale de I'Eclairage (CIE) chromaticity coordinates of Ba 3 (Y 0.75 Eu 0.25 ) 4 O 9 phosphors were measured to be (0.6695, 0.3302) which located at the red region, and significantly, the high color purity was about 97.9%. The as-synthesized phosphors also possessed excellent thermal stability and the activation energy was determined to be 0.29 eV. Therefore, the investigated results indicated that the Ba 3 Y 4 O 9 :Eu 3+ phosphor may be a suitable candidate as a red phosphor for white light-emitting diodes under effective excitation at near-ultraviolet and blue light., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

A series of Mn 4+ -activated CaLaMgSbO 6 far-red-emitting phosphors were synthesized by a solid-state reaction route and the microstructure and optical characterizations were investigated in detail. Upon excitation at 370 and 469 nm, the samples showed intense far-red emission at about 708 nm originating from the 2 E g → 4 A 2g transition and the optimal Mn 4+ concentration was 0.7 mol%. The as-prepared phosphors also exhibited excellent internal quantum efficiency (88%) and high thermal stability. The emission intensity at room temperature dropped to 54% when the temperature rose to 423 K and the activation energy was 0.34 eV. The outstanding optical properties and the fact that the emission band of the obtained phosphors had a broad overlap with the absorption band of phytochrome P FR demonstrated that the CaLaMgSbO 6 :Mn 4+ phosphors may be promising potential spectral converters for applying to indoor plant cultivation light-emitting diodes., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

In this paper, we reported on the high-efficiency and thermally-stable La 2 LiSbO 6 :Mn 4+ ,Mg 2+ (LLS:Mn 4+ ,Mg 2+ ) far-red emitting phosphors. Under 338 nm excitation, the composition-optimized LLS:0.3%Mn 4+ ,1.6%Mg 2+ phosphors which were made up of [SbO 6 ], [LiO 6 ], and [LaO 8 ] polyhedrons, showed intense far-red emissions peaking at 712 nm ( 2 E g → 4 A 2g transition) with internal quantum efficiency as high as 92%. The LLS:0.3%Mn 4+ ,1.6%Mg 2+ phosphors also exhibited high thermal stability, and the emission intensity at 423 K only reduced by 42% compared with its initial value at 303 K. The far-red light-emitting device has also been made by using the LLS:0.3%Mn 4+ ,1.6%Mg 2+ phosphors and a 365 nm emitting InGaN chip, which can emit far-red light that is visible to the naked eye. Importantly, the emission spectrum of the LLS:0.3%Mn 4+ ,1.6%Mg 2+ phosphors can match well with the absorption spectrum of phytochrome P FR , indicating the potential of these phosphors to be used in plant growth light-emitting diodes., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

A series of new red-emitting Ba 2 Lu 4.98- x Eu x La 0.02 B 5 O 17 (0.1 ≤ x ≤ 1.0) phosphors were synthesized via the high-temperature solid-state reaction method. The phase formation of the as-synthesized Ba 2 Lu 4.48 Eu 0.5 La 0.02 B 5 O 17 phosphor was confirmed by powder X-ray diffraction analysis. It was found that La 3+ doping resulted in the reduction of LuBO 3 impurities and thus pure phase Ba 2 Lu 5 B 5 O 17 was realised. The morphology of Ba 2 Lu 4.48 Eu 0.5 La 0.02 B 5 O 17 phosphors was studied by field emission scanning electron microscopy (FE-SEM). As a function of Eu 3+ concentration the photoluminescence spectra and decay lifetimes were investigated in detail. Under excitation at 396 nm, a dominant red emission peak located at 616 nm ( 5 D 0 → 7 F 2 ) indicated that Eu 3+ ions mainly occupied low symmetry sites with a non-inversion center in Ba 2 Lu 4.48 Eu 0.5 La 0.02 B 5 O 17 . The optimal Eu 3+ ion concentration was found to be x = 0.5 and the critical distance of Eu 3+ was determined to be 6.55 Å. In addition, the concentration quenching takes place via dipole-dipole interactions. The phosphors exhibited good CIE (Commission International de I'Eclairage) color coordinates ( x = 0.643, y = 0.356) situated in the red region and a high color purity of 97.8%. Furthermore, the internal quantum efficiency and the thermal stability of Ba 2 Lu 4.48 Eu 0.5 La 0.02 B 5 O 17 phosphors were also investigated systematically. The results suggest that Ba 2 Lu 4.48 Eu 0.5 La 0.02 B 5 O 17 may be a potential red phosphor for white light-emitting diodes., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Double perovskite-based LiLaMgWO 6 :Mn 4+ (LLMW:Mn 4+ ) red phosphors were synthesized by traditional solid-state route under high temperature, and they showed bright far-red emission under excitation of 344 nm. The crystal structure, luminescence performance, internal quantum efficiency, fluorescence decay lifetimes, and thermal stability were investigated in detail. All samples exhibited far-red emissions around 713 nm due to the 2 E g → 4 A 2g transition of Mn 4+ under excitation of near-ultraviolet and blue light, and the optimal doping concentration of Mn 4+ was about 0.7 mol%. The CIE chromaticity coordinates of the LLMW:0.7% Mn 4+ sample were (0.7253, 0.2746), and they were located at the border of the chromaticity diagram, indicating that the phosphors had high color purity. Furthermore, the internal quantum efficiency of LLMW:0.7% Mn 4+ phosphors reached up to 69.1%, which was relatively higher than those of the reported Mn 4+ -doped red phosphors. Moreover, the sample displayed good thermal stability; the emission intensity of LLMW:0.7% Mn 4+ phosphors at 423 K was 49% of the initial value at 303 K, while the activation energy was 0.39 eV. Importantly, there was a broad spectral overlap between the emission band of LLMW:Mn 4+ phosphors and the absorption band of phytochrome P FR under near-ultraviolet light. All of these properties and phenomena illustrate that the LLMW:Mn 4+ phosphors are potential far-red phosphors for applications in plant cultivation LEDs., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Eu 3+ -activated Ba 2 Y 5 B 5 O 17 (Ba 2 Y 5- x Eu x B 5 O 17 ; x = 0.1-1) red-emitting phosphors were synthesized by the conventional high temperature solid-state reaction method in an air atmosphere. Powder X-ray diffraction (XRD) analysis confirmed the pure phase formation of the as-synthesized phosphors. Morphological studies were performed using field emission-scanning electron microscopy (FE-SEM). The photoluminescence spectra, lifetimes, color coordinates and internal quantum efficiency (IQE) as well as the temperature-dependent emission spectra were investigated systematically. Upon 396 nm excitation, Ba 2 Y 5- x Eu x B 5 O 17 showed red emission peaking at 616 nm which was attributed to the 5 D 0 → 7 F 2 electric dipole transition of Eu 3+ ions. Meanwhile, the influences of different concentrations of Eu 3+ ions on the PL intensity were also discussed. The optimum concentration of Eu 3+ ions in the Ba 2 Y 5- x Eu x B 5 O 17 phosphors was found to be x = 0.8. The concentration quenching mechanism was attributed to the dipole-dipole interaction and the critical distance ( R c ) for energy transfer among Eu 3+ ions was determined to be 5.64 Å. The asymmetry ratio [( 5 D 0 → 7 F 2 )/( 5 D 0 → 7 F 1 )] of Ba 2 Y 4.2 Eu 0.8 B 5 O 17 phosphors was calculated to be 3.82. The fluorescence decay lifetimes were also determined for Ba 2 Y 5- x Eu x B 5 O 17 phosphors. In addition, the CIE color coordinates of the Ba 2 Y 4.2 Eu 0.8 B 5 O 17 phosphors ( x = 0.653, y = 0.345) were found to be very close to the National Television System Committee (NTSC) standard values ( x = 0.670, y = 0.330) of red emission and also showed high color purity (∼94.3%). The corresponding internal quantum efficiency of the Ba 2 Y 4.2 Eu 0.8 B 5 O 17 sample was measured to be 47.2%. Furthermore, the as-synthesized phosphors exhibited good thermal stability with an activation energy of 0.282 eV. The above results revealed that the red emitting Ba 2 Y 4.2 Eu 0.8 B 5 O 17 phosphors could be potential candidates for application in near-UV excited white light emitting diodes., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Blue-green dual-emitting phosphors Ca 3 Lu(GaO) 3 (BO 3 ) 4 :Ce 3+ ,Tb 3+ (CLGB:Ce 3+ ,Tb 3+ ) were synthesized via a traditional solid-state reaction method. The phase of the phosphors was characterized by X-ray diffraction and the luminescence properties were investigated using the excitation and emission spectra, decay curves, temperature-dependent emission spectra, CIE chromaticity coordinates, and the internal quantum efficiency. Under 345 nm UV light excitation, Ce 3+ singly doped CLGB phosphors presented intense blue light in the 350-550 nm wavelength region with a maximum peak at 400 nm. In sharp contrast, CLGB:Ce 3+ ,Tb 3+ phosphors showed both the blue and green emission wavelengths of Ce 3+ and Tb 3+ ions, respectively. The overall emission colors can be tuned from blue (0.164, 0.042) to green (0.331, 0.485) via increasing the concentration of Tb 3+ ions, due to the energy transfer (ET) from Ce 3+ ions to Tb 3+ ions. The optimal doping concentration of Tb 3+ ions in CLGB:Ce 3+ ,Tb 3+ phosphors was found to be 40 mol%. The mechanism of the ET from the Ce 3+ to Tb 3+ ions was demonstrated to be electric quadrupole-quadrupole interaction. The CLGB:0.04Ce 3+ ,0.40Tb 3+ sample possessed a high IQE of 54.2% and excellent thermal stability with an activation energy of 0.3142 eV when excited at 345 nm. The integrated emission intensity of CLGB:0.04Ce 3+ ,0.40Tb 3+ at 423 K was found to be about 74% of that at 303 K. Finally, under 300 mA driven current, the fabricated prototype white light-emitting diode showed CIE chromaticity coordinates of (0.3996, 0.3856) and high color rending index of 81.2. Considering all the above characteristics, the obtained CLGB:Ce 3+ ,Tb 3+ phosphors can be a type of multicolor emitting phosphor for application in white light-emitting diodes., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Single-component white-emitting phosphors are highly promising for applications in phosphor-converted white light-emitting diodes. In this paper, novel single-phase LiCa 3(1- x ) ZnV 3 O 12 :Eu 3+ ( x = 0-0.05) phosphors with tunable white emissions were prepared by a conventional solid-state reaction. The LiCa 3 ZnV 3 O 12 ( x = 0) phosphor showed an efficient self-activated bluish-green emission due to the V 5+ -O 2- charge transfer transition of the [VO 4 ] 3- groups, and possessed an intense broad excitation spectrum in the 250-400 nm wavelength range. Together with the [VO 4 ] 3- emission, the red emission of Eu 3+ ions was also observed in LiCa 3(1- x ) ZnV 3 O 12 :Eu 3+ phosphors. The energy transfer from the [VO 4 ] 3- groups to the Eu 3+ ions was studied. Importantly, the emission colors of LiCa 3(1- x ) ZnV 3 O 12 :Eu 3+ phosphors varied from greenish-blue to whitish and then to red with increasing Eu 3+ content and the white-light emission was realized in the single-phase phosphor of LiCa 3 ZnV 3 O 12 :0.003Eu 3+ by combining the [VO 4 ] 3- -emission and the Eu 3+ -emission. The energy-transfer efficiency from [VO 4 ] 3- groups to Eu 3+ ions in the LiCa 3 ZnV 3 O 12 :0.003Eu 3+ sample was determined to be about 52% and the internal quantum efficiency of the LiCa 3 ZnV 3 O 12 :0.003Eu 3+ phosphor was found to be about 41.5%. In addition, the CIE chromaticity coordinates of LiCa 3 ZnV 3 O 12 :0.003Eu 3+ were ( x = 0.3374, y = 0.3596), and the correlated color temperature was estimated to be about 5311 K., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Novel blue-green-emitting Ca 3 Gd(AlO) 3 (BO 3 ) 4 :Ce 3+ ,Tb 3+ phosphors were successfully synthesized via traditional high temperature solid reaction method. X-ray diffraction, luminescence spectroscopy, fluorescence decay time and fluorescent thermal stability tests have been used to characterize the as-prepared samples. The energy transfer from Ce 3+ to Tb 3+ ions in the Ca 3 Gd(AlO) 3 (BO 3 ) 4 host has been demonstrated to be by dipole-dipole interaction, and the energy transfer efficiency reached as high as 83.6% for Ca 3 Gd 0.39 (AlO) 3 (BO 3 ) 4 :0.01Ce 3+ ,0.6Tb 3+ . The critical distance was calculated to be 9.44 Å according to the concentration quenching method. The emission colour of the obtained phosphors can be tuned appropriately from deep blue (0.169, 0.067) to green (0.347, 0.494) through increasing the doping concentrations of Tb 3+ . Moreover, the Ca 3 Gd 0.39 (AlO) 3 (BO 3 ) 4 :0.01Ce 3+ ,0.6Tb 3+ phosphor possessed excellent thermal stability at high temperature, and the emission intensity at 423 K was about 87% of that at 303 K. Finally, the fabricated prototype LED device with a BaMgAl 10 O 7 :Eu 2+ blue phosphor, CaAlSiN 3 :Eu 2+ red phosphor, Ca 3 Gd 0.39 (AlO) 3 (BO 3 ) 4 :0.01Ce 3+ ,0.6Tb 3+ green phosphor and 365 nm-emitting InGaN chip exhibited bright warm white light. The current study shows that Ca 3 Gd 0.39 (AlO) 3 (BO 3 ) 4 :0.01Ce 3+ ,0.6Tb 3+ can be used as a potential green phosphor for white LEDs., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)