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Poor water stability is the main problem of commercialized Mn4+-doped fluorides for white light emitting diode (WLED) application. This work proposes a surface engineering strategy to rebuild a Mn4+-free fluoride shell on fluorides to effectively resist the destruction from water molecules. By simple processing using glyoxylic acid (GA) solution, the moisture resistance of the red-emitting fluorides can be significantly improved. The photoluminescence (PL) quantum efficiency (QE) of the surface-engineered K2SiF6:Mn4+ (KSFM-GA) still maintain 98.43% after water immersion for 360 h, in sharp contrary to the untreated one (its PLQE decreases to 59.79%). Additionally, PL intensity of the hydrolysed KSFM can be recovered to 99.1% through the treatment of the reducing GA solution. By using the high-stability KSFM-GA red phosphor, the as-fabricated high-performance warm-WLED device can still maintain 84.6% in luminous efficacy, higher than that (79.6%) with the untreated KSFM, after 500 hours of aging in a high temperature (85 oC) and high humidity (85%) environment.

Tb3+/Eu2+,3+-doped zinc aluminoborosilicate glasses were prepared using a conventional high temperature melt-quenching method. Infrared spectra and physical properties of as-prepared glasses verified that the addition of Tb/Eu causes structural weakness in the glass. Tuning of blue, green, and red emission bands achieves white light for the zinc aluminoborosilicate glasses. The broad blue emission band is attributed to the 5d-4f transition of Eu2+ due to partial reduction of Eu3+ during calcination in ambient atmosphere. The reduction of Eu3+ is related to the formation of Eu Zn • and V Zn '' defects and host alkalinity decreases with the addition of Eu3+. Emission spectra and decay curves confirm energy transfer from Tb3+ to Eu3+ in the zinc aluminoborosilicate glasses, and relative intensities of green and red luminescence can be tuned through concentrations changes of Tb3+ and Eu2+,3+. When the concentrations of Tb3+ and Eu2+,3+ are equal to 6% and 1.2%, respectively, a neutral white light emitting glass is obtained. Furthermore, the white-emitting glass shows very high thermal stability compared to a commercial Y3Al5O12:Ce3+ phosphor. Therefore, luminescence tuning of glasses through changing activator concentrations and energy transfer is expected to achieve high-powered white LEDs.

To pursue green ecological agriculture, long-life functionalized green house is looking for solar spectrum conversions with well spectral match, outstanding thermal and chemical stabilities, excellent anti-photobleaching and UV-conversion performance. CaS:Eu2+-based phosphors are widely known as a candidate for agricultural films with remarkable green-to-red conversion performance while they are also notorious for poor stabilities. In this work, a core-shell structured CaS:Eu2+@CaZnOS:Mn2+ composite phosphor was synthesized by a two-step solid state method. The coating layer of thermally and chemically inert oxysulfide prevents the sulfide core phosphor from hydrophilic, air-sensitive and heat-induced decompositions. Moreover, the addition of Mn2+ in CaZnOS shell qualifies the composite phosphor with strong UV absorption, which contributes to the improvement of the anti-photodegradation of the inner CaS:Eu2+ and the anti-aging of practical polymer films. The additional UV-to-orange red conversion resulting from CaZnOS:Mn2+ further extends the red components for the indoor plants. As a result, this dual UV/green excited and dual red-emitting super stable chalcogenide phosphor can be used as a general spectral conversion for plant cultivation.

Correction for ‘Achieving highly thermostable red emission in singly Mn2+-doped BaXP2O7 (X = Mg/Zn) via self-reduction’ by Song Li et al., Inorg. Chem. Front., 2022, 9, 3224–3232, https://doi.org/10.1039/D2QI00539E.

Cationic substitution is a prevalent strategy to tune the luminescence spectra of phosphors. In this work, we reported a series of Eu2+-activated whitlockite type Ca7Sr3.5-0.5xAx(PO4)7 (CSPA; A =Li, Na, K) (x = 0–1.00) phosphors. The substitution by Na+ for both half occupied/vacant M(4) site was verified via Raman spectra, Reitveld refinement and HR-TEM, whereas a similar accommodation of K+ into the Ca2Sr(PO4)2 (CSP) host cannot be realized due to the significant size mismatch. A continuous increase of Na+ contents led to the progressively structural contraction, promoting the migration of Eu2+ activator from looser M(4) to other sites, and regulating the luminescence behaviors. Consequently, the gradual red-shift of emission band terminated at a new yellow phosphor Ca7Sr3Na(PO4)7:0.04Eu2+. The cation vacancy repair developed in this work can not only migrate the Eu2+ activator among different cation sites, but also serves as a new strategy for tuning the luminescence properties of phosphor.

A series of emission color tunable Ce3+, Tb3+, and Eu3+ co-doped La2Si2O7 (LSO) phosphors have been prepared via a solid state reaction. The crystal structure, luminescence properties, and thermal stability of the phosphors were studied in this paper. There exists two kinds of energy transfer (ET) modes under UV excitation, namely, electric dipole-dipole interaction for Ce3+→Tb3+ and terbium bridge model [Ce3+→(Tb3+)n→Eu3+] for LSO:Ce3+,Tb3+,Eu3+ system. The emitting color of the phosphors can be tuned from green to yellow and eventually to orange-red through the Ce3+→Tb3+→Eu3+ energy transfer. Although codoping Tb3+ and Eu3+ into La2Si2O7:Ce3+ leads to the reduction of thermal stability, it still remains 80% for LSO:0.05Ce3+,0.8 Tb3+,0.02Eu3+ at 150 °C when compared to that at room temperature. The absolute quantum yield (QY) increases from 71.04% (LSO:0.05Ce3+) to 95.60% (LSO:0.05Ce3+, 0.6 Tb3+), while those of LSO:0.05Ce3+,yTb3+,0.02Eu3+ samples remain more than 70%. These results indicate that the phosphors can be candidates for application in phosphor-converted white light-emitting diodes (pc-WLEDs).

The Pr3+ doped CaTiO3 red emitting phosphor with enhanced PL and ultrahigh temperature sensing was prepared via NaF flux assisted solid-state reaction. All samples had the orthorhombic perovskite phase and no impurity was found. The typical sample mainly had sphere-like morphology with particle size of ∼670 nm. The optical bandgap values were ∼3.62–3.63eV. The Pr3+ quenching content was 0.6 mol% and the ET mechanism for quenching was the d-d interaction with the critical distance of 26.09 A. A certain amount of NaF flux could enhance red emission attributed to 1D2→3H4 transition owing to improving the crystallinity of phosphors and reducing point defects near Pr3+ through the substitution of O2− by F− and Ca2+ by Na+. The energy storage trap (oxygen vacancy) near IVCT state played the key role for trapping electrons, accounting for the LAG emission and the average depth of trap was 0.39 eV. The CIE chromaticity coordinates were very close to that of the ideal red light and the CP was as high as 99.98%. The maximal Sa and Sr was as high as ∼0.015 K-1 and∼ 5.2% K−1, respectively. The thermal induced relaxation between the 3Pj levels and 1D2 level through the IVCT state was supposed to account for the excellent optical temperature sensing. Our work may provide a useful inspiration for developing ultrahigh sensitive optical temperature sensors.

Ce3+ single-doped Ca3(SiO3)3 phosphors were synthesized by a traditional solid-state reaction at elevated temperature. The phase impurities of phosphors prepared at different conditions were characterized and analyzed and an optimal one was obtained. The synthesis and luminescent properties of the phosphors were studied in detail. As a result, two different emission bands can be observed under excitations at 330 and 360 nm, which peak at 380 and ∼400 nm, respectively. Further analyses of emission spectra reveal that there should exist four different emission bands originating from four Ce3+ luminescence centers on different Ca2+ sites. The phosphor with optimal Ce3+ content [Ca2.82(SiO3)3:0.18Ce3+] exhibits high absolute quantum efficiencies up to 90.1% and 79.5% for emission bands at 380 and 400 nm, respectively. Moreover, the emission intensity of Ca2.82(SiO3)3:0.18Ce3+ at 150 °C remains ∼65% of that at room temperature. The phosphor deserves further investigation for the purpose of application in pc-WLEDs.

Discovery of highly efficient and thermal stable phosphors is a major topic in phosphor-converted white light-emitting diodes (LEDs). A highly efficient and zero-thermal quenching blue-emitting phosphor is realized in nominal Km-0.4Al11O17+δ:0.2Eu2+, which benefits from rigid aluminate structure with space group P63/mmc and the introduction of trap energy levels. The internal and external quantum efficiencies of optimal nominal K1.6Al11O17+δ:0.2Eu2+ are 97.1% and 61.8%, respectively. The phosphor exhibits zero-thermal-quenching behavior within 150 °C. Further increasing K content results in even better thermal stability, however, lower quantum efficiency. The relationship between luminescence properties and crystal structure was discussed. Results suggest that the blue-emitting phosphor is a candidate for white phosphor-converted LEDs based on near-UV or violet chip.

A series of ZnS:KBr,x%Mn2+ (x = 0–0.25) phosphors with dynamic multicolor luminescence are obtained by simultaneously constructing strong host luminescence and heterochromatic doping emissive center in ZnS lattice. Under a fixed ultraviolet irradiation, the phosphors emit tunable colors ranging from cyan to yellow-orange with increasing x values gradually. Besides, those Mn2+-doped phosphor (x > 0) emits different colors under different UV excitations. After removal of the UV lamp, all ZnS:KBr,Mn2+ phosphors exhibit an orange afterglow that is different from its photoluminescence (PL) color. The dynamic PL and afterglow is associated with the interactions between two PL centers and traps in the material. Therefore, spatially and temporally resolved dynamic multicolor luminescence is realized by tuning doping concentration, excitation wavelength, and observation time, which features the ZnS:KBr,Mn2+ phosphors a great application potential in high-level secure anti-counterfeiting.

Poor humidity resistance is a bottleneck problem to be solved urgently for Mn4+ activated fluoride red phosphors. At present, some strategies such as outer coating, cation exchange (CE), and surface passivation (SP) have been developed, but the effect is limited. The key reason is that the easily hydrolyzed Mn4+ ions on the surface are difficult to be completely removed. With the goal of achieving a significant improvement in the moisture resistance of fluoride, this work proposes a new idea of using the reduction-assisted surface recrystallization (RSRC) strategy to construct a real core-shell structure without Mn4+ in the shell. The quantum efficiency (QE) of the K2SiF6:Mn4+ treated by the RSRC method is 99.95%. After boiling in water, the QE can even be maintained at 96.7%, which is significantly higher than that of the fluorides treated by CE (15.53%) or SP (62.64%) methods. The Mn-free shell is further determined by a combination of in-situ lift-out and STEM-EDX techniques. Finally, the aging results of LED devices in high temperature (85 °C) and high humidity (85%) environments further confirmed that the color stability of the K2SiF6:Mn4+ was significantly improved.

SnO2 micro/nano-structured biscuits had been successfully prepared via egg albumin-assisted sol–gel procedure. The typical sample calcined at 900 °C was pure SnO2 with a tetragonal rutile structure, constructed by the numerous pomegranate seed-like irregular nanoparticles in the range of ~100 to ~400 nm. The complexation of egg albumin and tin ions and the bonding characteristics of functional groups had been confirmed. The band gap energy values of samples were apparently higher than the reference value of bulk matter, which could be assigned to a well-known effect that small particles tended to exhibit increased band gaps. It was revealed that with the increase of the calcined temperature the photoluminescence efficiency increased. The sample at 500 °C had the higher photocatalytic activity and the higher mean photo-degradation rate of MO was 88.1 ± 1.2% as compared to other samples, which could be assigned to the lower value of band gap due to the defect levels in the band gap from the impurities formed during the growth and the lower photoluminescence efficiency, beneficial to electrons transfer and reducing the combination of electron and hole, which resulted in better photocatalytic activity.

Tb3+-doped and Eu2+, Tb3+ co-doped Ca9Y(PO4)7 phosphors were synthesized by conventional solid-state method. Additionally, the luminescence properties, decay behavior and energy transfer mechanism have already been investigated in detail. The green emission intensity of Tb3+ ions under NUV excitation is weak due to its spin-forbidden f-f transition. While Eu2+ can efficiently absorb NUV light and yield broad blue emission, most of which can be absorbed by Tb3+ ions. Thus, the emission color can be easily tuned from cyan to green through the energy transfer of Eu2+→Tb3+ in Ca9Y(PO4)7:Eu2+,Tb3+ phosphor. In this work, the phenomenon of cross-relaxation between 5D3 and 5D4 are also mentioned. The energy transfer is confirmed to be resulted from a quadrupole-quadrupole mechanism.

A range of Ca 10.5-1.5 x La x (PO 4 ) 7 :Eu 2+ phosphors were synthesized by high temperature solid state method. Subsequently we studied the crystal structures and luminescent properties through X-ray diffraction, photoluminescence and photoluminescence excitation, diffuse reflection spectra, Raman spectra and decay curves systematically. Based on the special crystal structure of β -Ca 3 (PO 4 ) 2 :Eu 2+ , its emission undergoes a variation from violet–blue to cyan through introducing La 3+ . The substitution of La 3+ for Ca 2+ could form some cation vacancies in Ca(4) sites according to the scheme 3Ca 2+ = 2La 3+ + □ due to the different ion valence, which compels Eu 2+ to migrate from Ca(4) site to other sites. Additionally, the formation of the cation vacancies can further reduce the thermal stability of phosphors.

Nominal composition phosphors BaZnSiO 4 :RE (RE = Eu, Tm, Sm, Yb) were synthesized by the conventional solid-state method in air (oxidizing atmosphere, OA) and under 10%H 2 /90%N 2 flow (reductive atmosphere, RA) conditions, respectively. Self-reduction phenomenon, which is a valence change from trivalent rare-earth ions (RE 3+ ) to corresponding divalent state (RE 2+ ) without reducing agent, were observed in the samples of Eu/Tm/Yb-doped BaZnSiO 4 but have not observed in Sm-doped samples. Compared with RA condition, the ca. percent of the reductive concentration of Eu 2+ /Tm 2+ /Yb 2+ in the phosphors BaZnSiO 4 prepared in OA condition are 21%, 15% and 35%, respectively. It was found that both of BaZnSiO 4 :Eu and BaZnSiO 4 :Tm prepared in air show greatly broad band emission peak at 500 nm under the excitation of ultraviolet (UV), which indicated they are potential phosphors for UV-based LED. The factors which are related to self-reduction degree have been also discussed. The successful synthesis of BaZnSiO 4 :RE 2+/3+ phosphors in air provides a new route to obtain other novel orthosilicate-based materials.

Ce 3+ , Mn 2+ codoped and Ce 3+ , RE 3+ , Mn 2+ (RE 3+ = Tb 3+ , La 3+ , Gd 3+ , Lu 3+ ) codoped Ca 5 (BO 3 ) 3 F phosphors have been synthesized by a high-temperature solid-state reaction. Crystal structure and site occupancy of the doped ions were determined by Rietveld refinement. Photoluminescence (PL) spectra as well as fluorescence lifetimes were investigated. Under the excitation of 360 nm, Ca 5 (BO 3 ) 3 F:Ce 3+ , Mn 2+ phosphors show a strong emission band at 392 nm and a very weak emission band at ∼630 nm, which belong to Ce 3+ and Mn 2+ , respectively. The introduction of Tb 3+ and even non-luminescent ions such as La 3+ , Gd 3+ and Lu 3+ to the Ce 3+ , Mn 2+ codoped phosphors leads to the enhancement of Mn 2+ emission. The analyses of fluorescence lifetimes suggest that there is energy transfer from Ce 3+ and especially Tb 3+ to Mn 2+ . However, Rietveld refinement results indicate that the introduction of RE 3+ ions leads to the adjustment of Mn 2+ ions from Ca(3) site to Ca(2) site, which is the key factor for the enhancement of Mn 2+ emission. The crystal-site engineering is expected to provide a promising route to tune the luminescent properties of phosphors with more than one site for activators.

Thermal stability and quantum efficiency are crucial parameters for phosphors when they act as components in phosphor-converted white light-emitting diodes (pc-wLEDs). Therefore, it is important to explore phosphors with highly thermal stability and quantum efficiency. Blue-emitting Ce3+-activated (Ba1-xSrx)3Y2(BO3)4 phosphors were synthesized through high-temperature solid-state reaction. X-ray powder diffraction suggests the success of complete solid solution in the phosphor series. Scanning electron microscope (SEM) image and elemental mapping suggest uniform distribution of Ba and Sr atoms in the phosphor particles. Rietveld refinement indicates that cell volume decreases with increasing the content of Sr2+, while the related emission peak exhibits a slight blue shift, which implies the existence of remote control effect. Both thermal stability and quantum efficiency increase with the evolution of solid solution from Ba3Y2(BO3)4:Ce3+ to Sr3Y2(BO3)4:Ce3+, which is due to the increase of structural rigidity. The emission intensity of Sr3Y1.94(BO3)4:0.06Ce3+ at 423 K remains ∼56% of the room-temperature value. The internal and external quantum efficiencies of Sr3Y1.94(BO3)4:0.06Ce3+ are ∼93% and ∼67%, respectively. A pc-wLED was fabricated with a 365 nm UV chip, Sr3Y1.94(BO3)4:0.06Ce3+, commercial green phosphor, and commercial red phosphor, which exhibits a color rendering index of 94.5. This work provides an example on the adjustment of luminescent properties through solid solution.

Thermally stable phosphors are crucial for the application in phosphor-converted white light-emitting diodes. This paper reports the evolution of phase compositions in nominal Na2−xAl2B2O7:xEu (x = 0.02–2.0) upon replacing Na atoms by Eu atoms. Eu2+-activated blue-emitting phosphor was discovered through phase segregation combined with related analyses. The structure, phase composition and related luminescent properties were investigated by X-ray powder diffraction, backscattered electron image combined with elemental mapping, cathodoluminescence-combined scanning electron microscope, and temperature-dependent emission spectra, etc. Analyses results suggest that EuBO3 phase segregates upon the gradual replacement of Na by Eu atoms, which is accompanied by phase transformation from Na2Al2B2O7:Eu2+ to NaAl11O17:Eu2+ and dramatic enhancement of blue emission. The broad emission band is peaking at around 470 nm under UV irradiation. The internal quantum efficiencies of nominal Na0.4Al2B2O7:1.6Eu and Na0.2Al2B2O7:1.8Eu are 58.6% and 60.2%, respectively, which contain both NaAl11O17 and EuBO3 phase. The emission intensity for these two samples at 150 °C remains 96% (x = 1.6) and 83% (x = 1.8) of the room-temperature values, respectively.

High quantum efficiency is a vital parameter of phosphors for practical application. An efficient near-UV and blue emitting phosphor Li4SrCa(SiO4)2:Ce3+ was synthesized by a traditional solid-state reaction, and luminescent properties were studied in detail. The Ce3+-activated phosphor can emit both a near-UV light centred at 345 nm and a blue light peaking at 420 nm when Ce3+ occupies the Sr and Ca site, respectively. The internal quantum efficiency (IQE) of Li4SrCa(SiO4)2:0.03Ce3+ is as high as 97% under the excitation at 288 nm, while the external quantum efficiency (EQE) is 66%. The IQE and EQE values of Li4SrCa(SiO4)2:0.03Ce3+ under the excitation at 360 nm are 82% and 31%, respectively.

In this paper, Ce3+ doped and Ce3+, Tb3+ co-doped Ca5(BO3)3F phosphors were synthesized by a high-temperature solid-state reaction. Upon excitation at 360 nm, the emission spectra of Ce3+ doped phosphors exhibit a broad emission band peaking at 392 nm, which originates from the 5d to 4f transition of Ce3+. The Ce3+, Tb3+ co-doped phosphors show strong energy transfer from Ce3+ to Tb3+, and the emission color can be tuned from purplish blue to green by changing the Tb3+ content. The excitation band in the 300–400 nm region broadens when monitored at 541 nm compared to that monitored at 392 nm. Furthermore, the co-doping of Tb3+ facilitates the appearance of green emitting Ce3+, which originates from Ce3+ on the Ca site other than that for purplish-blue Ce3+. The relationship between the luminescence properties of Ce3+ and its coordination environments, namely, different Ca sites, is discussed based on the calculations of centroid shift and crystal field splitting of 5d energy levels of Ce3+. Results suggest that Ce3+, Tb3+ co-doped Ca5(BO3)3F phosphors may be a candidate for near-UV chip based white light-emitting diodes.

Photoluminescence evolution in single-composition phosphors for solid state lighting can be realized through an energy transfer strategy, which is commonly based on one sensitizer and one activator. In this work, we focus on a dual energy transfer process, that is, energy transfers from the sensitizer Eu2+ at two different cation sites to the activator Mn2+ at another site in whitlockite-type β-Ca2.7Sr0.3(PO4)2. Firstly, we refined the crystal structure of the β-Ca2.7Sr0.3(PO4)2 host by a Rietveld method. Then we studied the phase, morphology and photoluminescence of Eu and Mn co-activated β-Ca2.7Sr0.3(PO4)2 phosphors, which are synthesized by a conventional solid-state reaction. By adjusting the ratio of Eu2+/Mn2+, the emission hue can be controlled from cyan (0.211, 0.281) to white-light (0.332, 0.290) and eventually to red (0.543, 0.276). The dual energy transfers from Eu2+ to Mn2+ are demonstrated to be dipole–dipole and quadrupole–quadrupole mechanisms, respectively. Moreover, white light-emitting diodes (LEDs) were fabricated through the integration of a 375 nm NUV chip and the white-emitting phosphor Ca2.7Sr0.3(PO4)2:0.008Eu2+, 0.03Mn2+ into a single package, which shows a warm white light with color coordinates of (0.40, 0.41) and correlated color temperature of 3731 K.

Eu2+ and Mn2+ coactivated β–Ca3(PO4)2 (TCP) phosphors have been prepared by high-temperature solid-state reaction. The site occupation and photoluminescence properties of Eu2+ and Mn2+ have been identified and discussed in detail. The energy transfer from Eu2+ to Mn2+ in TCP: Eu2+, Mn2+ phosphors has been validated and demonstrated to be a resonant type via a dipole-quadrupole mechanism, and the critical distance (RC) calculated by concentration quenching method is 21.76 A. A color-tunable emission from violet-blue to red in TCP: Eu2+, Mn2+ phosphors can be realized via the energy transfer from Eu2+ to Mn2+ ions.

Eu 2+ -doped Li 4 SrCa(SiO 4 ) 2 phosphor was synthesized by a high temperature solid-state reaction. There are two different crystallographic sites, namely, a Sr 2+ site and a Ca 2+ site in the cell of Li 4 SrCa(SiO 4 ) 2 , which can be occupied by Eu 2+ ions and will generate two emission bands. However, three different emission bands were observed in this phosphor. The first one is peaking at 433 nm with the corresponding excitation band at 250–400 nm. The second one is at 584 nm under the excitation at 395 nm, which shows lower emission intensity than that of the blue emission. The third one is at around 615 nm under the excitation at 460 nm. Analysis suggests that the 433 nm emission belongs to Eu 2+ on Sr 2+ site, and the 584 nm emission originates from Eu 2+ on isolated Ca 2+ site. The 615 nm emission may be related to Eu 2+ clusters.

Enhanced photoluminescence and high temperature sensitivity of a novel Pr3+ doped SrSnO3/SnO2 composite phosphor was investigated. The typical samples had SrSnO3 and SnO2 phases and spherical morphology with mean particle size of 421 nm. The presence of SnO2 phase could contribute to improving crystallinity of SrSnO3. The optical bandgap values of Pr3+ doped SrSnO3/SnO2 composite phosphors were in the range of ~3.85–~3.88 eV. Enhanced photoluminescence intensity of the typical Pr3+ doped SrSnO3/SnO2 composite phosphor was attributed to the effective energy transfer from host material to Pr3+ ions. The typical samples had the greenish-blue emission. The d-d or d-p interaction could explain the Pr3+–Pr3+ energy transfer mechanism. The activated energy value was 0.206 eV for SrSnO3: 0.6%Pr3+ phosphor and 0.429 eV for SrSnO3/SnO2: 0.16%Pr3+ composite phosphor. The maximum relative sensitivity of SrSnO3/SnO2: 0.16%Pr3+ was estimated to be 5.727% K−1 at 303 K (5257.83/T2), which was very prominent and excellent, compared with that of SrSnO3: 0.6%Pr3+, for temperature sensitivity application. The possible mechanism for the greenish-blue emission and the thermal quenching process of 3P0 level through IVCT state were proposed from the configurational coordinate diagram.

A single-phase multicolor emitting phosphor, Ca3Al2O6:Ce3+,Li+, was prepared by a solid-state reaction. When the Ce3+ concentration is lower than 0.030 (molar ratio in Ca3Al2O6), yellow and greenish blue emissions can be observed under the excitation by a blue and a near UV light, respectively. The yellow-emitting phosphor possesses an internal quantum efficiency of 89%. Additional purplish blue emission turns up when Ce3+ concentrations are higher than 0.040. Tunable emission bands are originated from Ce3+ ions on different Ca sites in Ca3Al2O6. Although the emission band of purplish blue or greenish blue overlaps the excitation band of yellow emission, and the distances between the unlike Ce3+ ions are in the range of electric dipole–dipole interaction, no energy transfer is observed. Furthermore, emission wavelengths for the yellow, greenish blue, and purplish blue emission show little change upon increasing Ce3+ concentrations.

The red-emitting phosphor CaZnOS:Eu 2+ was synthesized from CaCO 3 , ZnS, Eu 2 O 3 and CeCl 3 by controlling the sintering condition. It was found that Ce 3+ ions can play a role of reductant to contribute to the formation of Eu 2+ in CaZnOS matrix under inert protective atmosphere. While the gas flow changed to H 2 /N 2 , the product turned to CaS easily. XRD, photoluminescence spectra, UV–vis and IR absorption spectra were evaluated to investigate the origin of the distinctions of the optical properties and stabilities between the two divalent europium ions doped phosphors CaZnOS:Eu 2+ and CaS:Eu 2+ . The similarities and differences between them were analyzed.

Effects of ZrO 2 , La 2 O 3 , CeO 2 , Yb 2 O 3 and V 2 O 5 on the crystallization kinetics, microstructure and mechanical properties of mica glass–ceramics were investigated by the differential scanning calorimetry (DSC), X-ray diffractometry (XRD), scanning electron microscopy (SEM) and microhardness tester. Results show that bulk crystallization can be obtained by introducing proper nucleation agents into the glass. Both Ozawa method and Kissinger method are suitable for analyzing the crystallization kinetics of mica glass–ceramic. The addition of nucleation agents has little influence on the value of n , keeping two-dimensional crystal growth mechanism. ZrO 2 and V 2 O 5 are best nucleation agents in mica system. The increase of crystallization temperature is helpful for the increase of aspect ratio, and the microstructure of the glass–ceramics becomes interconnected, which contributes the improvement of the machinability of the glass–ceramics. Microhardness ( H v ), cutting energy ( μ 1 ) and machinability parameter ( m ) can be used for estimating the machinability of mica glass–ceramics.

Based on the idea that modification of light quality could realize the modulation of morphogenesis and growth rate of plants, we fabricate a near ultraviolet (NUV)-green to red spectral converting BaY2S4:Eu2+, Er3+ phosphor by a solid state reaction route. We herein investigated the crystal structure and photoluminescence properties of the compounds in details. The incorporation of Eu2+ ions does not only enhance the red emission of Er3+ tenfold, but also broadens the absorption region of phosphor. Photoluminescence and decay curves confirm the energy transfer from the host lattices and Eu2+ ions to Er3+ ions. The optimized compositions have strong absorption in the NUV-green region and show intense luminescence at 600 and 663 nm, which matches well with the absorption spectrum (red region) of chlorophyll a. On the basis of the experiment results, a possible luminescent mechanism for the red-emitting BaY2S4:Eu2+, Er3+ phosphor is proposed. We believe this new NUV-green to red spectral converter may open a new route to the design of advanced phosphors for agricultural applications.