Search

Partial replacement of K+ by Sr2+ in Eu-doped K-beta-alumina changes the trap content and structural rigidity, which facilitates the variation from anti-thermal quenching to zero thermal quenching within 150 °C.

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.

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.

Due to the wide compositional variability and structural tolerance, Eu2+-doped whitlockite β-Ca3(PO4)2 (TCP)-type phosphors with different visible emissions have been realized by manipulating the chemical compositions. However, the site preference of the dopant Eu2+ at the multi-cation sites has been a dispute recently. In this study, a combination of experimental and theoretical calculations was applied to identify the preferential occupancy and variable optical behavior of Eu2+ through the evolution of Ca10.5−0.5xKx(PO4)7 (0 ≤ x ≤ 1) isostructures. Both spectral analysis and theoretical calculations reveal that Eu2+ prefers to occupy the loose Ca(4) sites and produce a narrow band emission around 420 nm. Moreover, a continuous increase in the K content compels the redistribution of dopants from the Ca(4) into the Ca(3) site, resulting in an abrupt spectral shift to 470 nm. Moreover, a vacancy defect repair effect was proposed for the enhancement in the luminescence of Ca10.5−0.5xKx(PO4)7:Eu2+, in which the incorporation of K+ repaired the half-unoccupied Ca(4) sites and benefitted the reduction of Eu3+ to Eu2+. Moreover, to further prove the significant vacancy repair and dopant redistribution effects, Na+- and Li+-doped systems were investigated. In addition, together with the reported Sr2+- or Gd3+-doped systems, the preferential occupancy and saltatory spectral variations of Eu2+ in whitlockite-type phosphors were uniformly clarified by cationic modification events.

With outstanding green-to-red spectral conversion ability, CaS:Eu2+ is notorious for its poor chemical and thermal stabilities, which seriously limit its practical applications. Herein, we structure core–shell CaS:Eu2+@CaZnOS phosphors by a convenient solid-state method. The oxysulfide protection layer was formed due to inward incorporation of ZnO into the surface lattice of the CaS substrate. As a result, the surface modified chalcogenide red phosphor shows super stability toward acidic/basic solutions and retains its brightly emissive activity in aqueous solutions with pH = 1–14. Moreover, it exhibits the best thermal resistance behavior for alkaline earth sulfide-based phosphors up to now, maintaining over 95% of the emission intensity till 150 °C. In addition, the QE of the optimal core–shell phosphor in the green region reached 68.78%, which is elevated by ∼23% compared to that of the starting CaS:Eu2+. This is the first time to simultaneously realize a chemically and thermally stable sulfide phosphor, along with high QE, which exhibits good suitability for solar spectral conversion films and light-emitting diodes for facilitating plant growth.

Phosphor-converted white light-emitting diodes (w-LEDs) have become the new generation of lighting. Several strategies have been introduced to realize a high CRI value for illumination. However, these strategies suffer from new problem(s), such as reabsorption, different deterioration rates among the phosphors, different thermal stability for diverse emission bands, and/or the decrease of quantum efficiency for the phosphor. Therefore, it is desired to develop new phosphors that not only realize a high CRI value for w-LEDs, but also resolve the above problems. In this work, a site-preference driven color-tunable Eu2+-activated K2Ca(PO4)F phosphor was prepared. The color-tunable phosphor exhibits two broad emission bands peaking at 485 and 660 nm upon UV excitation. White emission is realized in K2Ca(PO4)F:0.006Eu2+. The internal and external quantum efficiencies of the white-emitting phosphor are 91.5 and 66.9%, respectively. The phosphor also exhibits good thermal stability, namely, the emission intensity at 423 K maintains >80% of that at room temperature, and the intensity ratio between the two emission bands remains nearly unchanged within 423 K. A white LED device has also been fabricated using a 365 nm LED chip and K2Ca(PO4)F:0.006Eu2+, showing a high color rendering index (Ra = 87.6). These results indicate that the K2Ca(PO4)F:Eu2+ phosphor is a promising candidate for UV-pumped w-LEDs.

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.

Ba1.8–xSrxSiO4:0.1Ce3+,0.1Na+ (x = 0–1.8) phosphors were prepared by a high-temperature solid-state reaction. The emission peaks of Ba1.8–xSrxSiO4:0.1Ce3+,0.1Na+ shift from 391 to 411 nm with increasing Sr2+ content under excitation by a UV light at around 360 nm. Ba0.4Sr1.4SiO4:0.1Ce3+,0.1Na+ phosphor exhibits the best performance of luminescence, whose absolute quantum efficiency is 97.2%, and the emission intensity at 150 °C remains 90% of that at room temperature. The effect of replacing Ba2+ by Sr2+ on the red shift of the emission band and the increase of quantum efficiency (QE) and thermal stability (TS) was investigated in detail based on the Rietveld refinements, Raman spectra, thermoluminescence, and decay curves, etc. The performance of UV chip-based pc-LEDs indicates that Ba0.4Sr1.4SiO4:0.1Ce3+,0.1Na+ can be a promising blue phosphor for white-emitting pc-LEDs.

Many approaches have contributed to improving the luminescence properties of phosphors, including surface coating, direct reduction and charge compensation, which are involved in reducing the inner or surface defects of luminescent particles. In this study, we propose a cation vacancy repair strategy to successfully improve the orange-yellow luminescence properties of the Sr9Mg1.5(PO4)7:Eu2+ phosphor. The main idea of the strategy is that introducing K+ repairs the vacancy at the Mg(1) site according to the formula . The preferred substitution of the large Mg(1) site by K+ is supported by theoretical calculations. As a result, the luminescence of the repaired phosphate phosphor was enhanced by 2.5 times, and the internal and external quantum efficiency significantly increased by 50.5% and 55.4%, respectively. Additionally, the thermal stability was also a little improved. The enhancement mechanisms for luminescence are discussed in detail based on investigations of the microstructure, luminescence spectra, decay curves and concentration using various analysis techniques. We find that low luminescence efficiency is due to the existence of vacancy defects in the phosphor. Through using the repaired Sr9MgK(PO4)7:Eu2+ phosphor, a white LED package demonstrated a low correlated color temperature (∼2900 K), high color rendering index (∼90) and R9 > 91. We expect that the strategy proposed herein would improve luminescence for other phosphors with vacancy defects.

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.

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.

A series of Ca2Sr(PO4)2:Ce3+,Mn2+,Na+ phosphors were synthesized by a high-temperature solid-state reaction. Under ∼320 nm excitation, the Ce3+ and Mn2+ co-doped phosphors exhibit two emission bands peaking at 370 and 645 nm, which originate from 5d–4f and 3d–3d transitions of Ce3+ and Mn2+, respectively. Luminescence properties, diffuse reflectance spectra, and decay curves indicate that energy transfer (ET) occurs from Ce3+ to Mn2+, and the ET efficiency reaches its maximum (91%) at an Mn2+ content of 0.35. The diffuse reflectance spectrum shows that the co-doped phosphors have strong absorption around 320 nm, which is good for the anti-aging ability of an agricultural film. The absolute quantum efficiency of the Ca1.6Sr(PO4)2:0.15Ce3+,0.10Mn2+,0.15Na+ phosphor is ∼94%. And the co-doped phosphors exhibit good stability in water. Therefore, Ca2Sr(PO4)2:Ce3+,Mn2+,Na+ phosphors have potential application as a light conversion material in agricultural films.

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.

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, a novel intermediate phase transition metathesis strategy is adopted to prepare Eu2+-doped CaS-based materials on the basis of green chemistry. ZnS acts as a vulcanizing agent and contributes to the formation of CaS from CaO through thermal decomposition of an intermediate state of CaZnOS. The recycling of zinc content is realized by collections of zinc evaporation during the process at high temperature. Few atoms would be wasted and no hazardous auxiliaries are used or produced. Meanwhile, solid solubilities of Mg, Sr and Ba in the CaS compound are verified quite different from the previous results in this case. The effect of Sr/Ca ratios on the luminescence properties of (Ca,Sr)S:Eu2+ phosphors is also investigated. A solar energy conversion laminated glass is promoted to overcome the drawback of decomposition of phosphors to moisture and recycling of agriculture films, which provides a promising permanent functional green-to-red sunlight spectrum conversion greenhouse device for green agriculture.

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.