Solvent extraction of nickel and cobalt by mixtures of carboxylic acids and non-chelating oximes

The effect of non-chelating oximes on the solvent extraction of nickel(II) and cobalt(II) by solutions of carboxylic acids (H₂A₂) in xylene has been studied. Synergistic enhancements of extraction were found with aldoximes, but not with ketoximes. The synergistic effects are larger for nickel than for cobalt, with the result that the selectivities of the carboxylic acids for nickel over cobalt are considerably enhanced in the presence of aldoximes. The influence of the molecular structure of the oxime and carboxylic acid components upon the synergistic effects is rationalized in terms of the prevailing stereochemical and electronic effects. The extracted complexes were shown to be octahedral in structure, with the compositions NiA₂(oxime)₄ and CoA₂(oxime)₄.The mixed reagent systems may prove useful for the selective extraction of nickel in the presence of cobalt.     

Synergistic extraction of rare earth by mixtures of 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester and di-（2-ethylhexyl） phosphoric acid from sulfuric acid medium

The extraction of Nd^3＋ and Sm^3＋, including the extraction and stripping capability as well as the separation effect of Nd^3＋ or Sm^3＋, from a sulfuric acid medium, by mixtures of di-（2-ethylhexyl） phosphoric acid （HDEHP, H2A2（0）） and 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester （HEH/EHP, H2L2（0）） were studied. The distribution ratios and synergistic coefficients of Nd^3＋ and Sm^3＋ in different acidities were also determined. A synergistic extractive effect was found when HDEHP and HEH/EHP were used as mixed extractants for Sm^3＋ or Nd^3＋. The chemical compositions of the extracted complex were determined as Nd.（HA2）2-HL2 and Sm.（HA2）2-HL2. The extraction equilibrium constants, enthalpy change, and entropy change of the extraction reaction were also determined.     

Solvent extraction of cobalt and nickel by organophosphorus acids I. Comparison of phosphoric,phosphonic and phosphonic acid systems

The solvent extraction of cobalt(II) and nickel(II) by xylene solutions of commercial dialkyl-phosphoric (D2EHPA), phosphonic (Shell RD 577) and phosphinic acids (Cyanex CNX) has been investigated. In each case, cobalt is extracted at lower pH values than nickel; under comparable conditions, the cobalt-nickel separation increases in the order phosphoric < phosphonic < phosphinic acids. Application of the slope analysis technique indicates stoichiometries of Co(HA₂)₂ and NiHA₂)₂(H₂A₂)_x(H₂O)2?x for the cobalt and nickel complexes, respectively, where H₂A₂ represents the dimerized extractant molecule and x = 0, 1, or2. The effect of a range of organic phase additives has been examined. Typical emulsion inhibiting reagents such as isodecanol and tributyl phosphate cause the cobalt—nickel separations to decrease significantly. A novel synergistic effect has been found with mixtures of D2EHPA and 2-ethylhexanal oxime (EHO); the synergism is so marked in the case of nickel as to reverse the selectivity for cobalt over nickel shown by D2EHPA alone. The electronic spectra of the organic extracts show that the organophosphorus acids examined from complexes of tetrahedral structure with cobalt and octahedral structure with nickel. In the D2EHPA—EHO system, however, the deep blue tetrahedral cobalt-D2EHPA complex is transformed into a pink octahedral complex, presumably of the type Co(HA₂)₂(EHO)₂, whilst the green octahedral nicke—D2EHPA complex is converted to a bright blue species of similar geometry, in which the neutral oxygen-donor ligands (H₂A₂ and/or H₂O) have been displaced by the nitrogen-donor oxime ligands.     

Aliphatic Non-Chelating Aldoximes as the Effective Extractants for Recovery and Separation of Nickel and Cobalt from Halide and Thiocyanate Solutions

Nickel recovery from solutions containing nickel and cobalt is a problem because the cobalt oxidation in the organic phase and the slow rate of nickel extraction, or small value of separation coefficient (β_Ni/Co) are characteristic of many extraction systems suggested for this purpose. The extraction systems with aliphatic non-chelating aldoximes do not have the above-mentioned shortcomings.

The extraction of metal halides from acid solutions by aliphatic aldoximes occurs by coordination. Cobalt in extracts does not oxidize during a day or more. The extraction and stripping equilibriums are reached in 2-5 min. During extraction, Ni and Co do not form mixed extraction complexes. β_Ni/Co increases with halide-ions concentration rising in aquoeus phase and is approximately equal to 100 at their concentration > 3 M/l. From chloride to bromide solutions the distribution coefficients of Ni and Co (D_Ni, D_Co) decrease, but β_Ni/Co does not decrease. In extraction from thiocyanate solutions D_Ni, D_Co and β _Ni/Co reach the values comparable with the same in extraction from chloride solutions, but the process of metal extraction is accompanied by co-extraction of HSCN. The dependence of Ni recovery on out-salting cation has been investigated. Ni recovery has been shown to increase in the order: Na⁺ < Ca²⁺ < Al³⁺, which could have resulted from increasing of hydration energy of out-salting cation.

Rising of the chain length of alkyl radical in the order: heptaloxime, nonaloxime, decaloxime, 2-methyldecaloxime brings some decrease of D_Ni and D_Co, however does not influence the β_Ni/Co value.

The optimum conditions for extraction separation of Ni and Co by aldoximes from halide and thiocyanate solutions have been determined.     

A single-phase full-color phosphor Sr2Ca2La(PO4)3O:Eu2+,Tb3+,Mn2+: Photoluminescence and energy transfer

A single-phase full-color emitting phosphor Sr₂Ca₂La(PO₄)₃O:Eu²⁺,Tb³⁺,Mn²⁺ was synthesized by the high temperature solid-state method. The phase formation, luminescence properties, thermal stability, and energy transfer from Eu²⁺ to Tb³⁺ and Eu²⁺ to Mn²⁺ in Sr₂Ca₂La(PO₄)₃O were investigated in details. Tunable emission color from blue to blueish green or orange can be observed under 365 nm near-ultraviolet excitation based on the energy transfer from Eu²⁺ to Tb³⁺ or Mn²⁺ ions by varying the ratio of Eu²⁺/Tb³⁺ or Eu²⁺/Mn²⁺ ions. White light was obtained with chromaticity coordinates of (0.3558, 0.3500) in the Sr₂Ca₂La(PO₄)₃O:0.04Eu²⁺,0.08Tb³⁺,0.40Mn²⁺ phosphor, suggesting their potential applications in white light emitting diodes.     

Tunable emission properties of tri-doped Ca_9LiY_(2/3)(PO_4)_7:Ce~(3+),Tb~(3+),Mn~(2+) phosphors with warm white emitting based on energy transfer

Tri-doped Ca_9 LiY_(2/3)(PO_4)_7:Ce~(3+),Tb~(3+),Mn~(2+)phosphors were prepared by a high-temperature solid state method.Under UV light excitation,Ca_9 LiY_(2/3)(PO_4)_7:Ce~(3+)samples exhibit a broad band ranging from 320 to 500 nm.At 77 K,the emission spectra of Ca_9 LiY_(2/3)(PO_4)7:Ce~(3+)samples present two obvious emission peaks,indicating that Ce~(3+)ions occupy two different kinds of lattice sites(Ca(1/2) and Ca(3)),As a good sensitizer for Tb~(3+),Ce~(3+)ions in Ca_9 LiY_(2/3)(PO_4)_7 lattice can effectively transfer part of energy to Tb~(3+),and the energy trans fer mechanism is determined to be dipole-dipole interaction.Consequently,the emitting color for Ce~(3+) and Tb~(3+) co-doped Ca_9 LiY_(2/3)(PO_4)_7 samples can be tuned from bluish violet to green.In order to further enlarge the emission gamut,Mn~(2+)ions as red emission components were added,forming tri-doped single-phase Ca_9 LiY_(2/3)(PO_4)_7:Ce~(3+),Tb~(3+),Mn~(2+)phosphors.The Ca_9 LiY_(2/3)(PO_4)_7:Ce~(3+),Tb~(3+),Mn~(2+)phosphors exhibit tunable emission properties through controlling the relative doping concentration of Ce~(3+),Tb~(3+)and Mn~(2+).Especially,Ca_9 LiY_(2/3)(PO_4)_7:0.09 Ce~(3+),0.12 Tb~(3+),0.30 Mn~(2+)can emit warm white light.The sample shows good thermal stability.At 150℃,the emission intensity for Ce~(3+)(360 nm),Tb~(3+)(545 nm) and Mn~(2+)(655 nm) decreases to 63%,69%,and 72% of its initial intensity,respectively.Moreover,the sample obtains good stability after 10 cycles between room temperature and150℃.     

Site occupation and energy transfer in full color emitting phosphor Ba2Ca(BO3)2:Ce3+(K+),Eu2+,Mn2+

White light-emitting diodes (WLEDs) fabricated by single-phase full color emitting phosphor are an emerging solution for health lighting. The crystallographic site occupation of activators in a proper host lattice is crucial for sophisticated design of such phosphor. Here, we report a high quality white light-emitting phosphor Ba₂Ca(BO₃)₂:Ce³⁺(K⁺),Eu²⁺,Mn²⁺ with spectral distribution covering whole visible region. Blue light emission originates from Ce³⁺ ions occupying preferentially Ba²⁺ site by controlling synthesis conditions. Green and red lights are obtained from Eu²⁺ occupying Ba²⁺ (and Ca²⁺) site and Mn²⁺ occupying Ca²⁺ site, respectively. In this triple-doped phosphor, strong red emission with a low concentration of Mn²⁺ is realized by the efficient energy transfer from Ce³⁺ and Eu²⁺ to Mn²⁺. Furthermore, high quality white light is accomplished by properly tuning the relative doping amount of Ce³⁺(K⁺)/Eu²⁺/Mn²⁺ based on efficient simultaneous energy transfer. The results indicate that Ba₂Ca(BO₃)₂:Ce³⁺(K⁺),Eu²⁺,Mn²⁺ is a promising white light-emitting phosphor in WLEDs application.     

Solvent extraction equilibria of copper and nickel with SME 529

Distribution equilibria in the extraction of copper and nickel from 1.0 mol/dm³ aqueous ammonium nitrate solution by anti-2-hydroxy-5-nonylacetophenone oxime, the active species of SME 529, in MSB 210 diluent were studied at 30°C. The extraction equilibrium constants for copper and nickel were determined to be 1.9 × 10¹ and 3.2 × 10⁵, respectively. The aqueous solubility of the oxime was also examined, resulting in a measurement of the partition coefficient of the monomeric oxime between the aqueous and organic phases, its dissociation constant in the aqueous phase and its dimerization constant in the organic phase as 2.2 × 10^?4, 0.53 nmol/dm³ and 31 dm³/mol, respectively. It was found that the extraction of copper is decreased by the addition of p-nonylphenol due to adduct formation. The equilibrium constant of the adduct formation between the oxime and p-nonylphenol was determined to be 6.6 dm³/mol. It was observed that nickel is extracted by p-nonylphenol.     

The extraction of nickel from ammoniacal media and its separation from copper,cobalt and zinc using hydroxyoxime extractants I. SME-529

Nickel extraction from ammoniacal media, containing, initially, 0.03 mol dm^?3 of nickel, by 10% v/v Shell metal extractant 529 in MSB 210 or Shellsol A, has been studied as a function of pH, counter anions (nitrate or sulphate), ammonium salt concentration, temperature (10 to 50°C), and the presence of copper, cobalt and zinc. The extraction of copper as a function of pH was studied in the presence of nickel. The pH for maximum nickel extraction decreased from 8.2 to 7.4 as the ammonium sulphate concentration increased from 0.1 to 3.4 mol dm^?3. Nickel extraction was lower from sulphate than from nitrate media and with Shellsol A, and at higher temperature. The enthalpy and entropy of extraction were negative. The presence of copper, cobalt and zinc decreased nickel extraction. Separation factors between copper and nickel are reported as a function of pH and indicate that initial removal of copper is desirable.From a consideration of the equilibrium, the extraction of nickel (with MSB 210 diluent) at 25°C could be expressed by the equation:

$\text{log}\text{D}{}_{\mathrm{<mtext>Ni</mtext>}}\text{= ?9.25 +}\text{log}\text{α}{}_0\text{+ 2}\text{log}\text{(C}{}_{\mathrm{HR}}\text{?2[}\text{Ni}\text{]}{}_{\mathrm{<mtext>org</mtext>}}\text{) + 2}\text{pH}$

where D_Ni represents nickel distribution coefficient, C_HR the total extractant concentration, [Ni]_org the organic nickel concentration (both in mol dm^?3) and α₀, the fraction of uncomplexed nickel in the aqueous phase calculated from the overall stability constants of Ni(NH₃)_i²⁺ complexes and the formation constant of NiSO₄ ion pairs.The limiting slope of ?1 for long D_Ni versus log [NH₃]_free plots indicated an average co-ordination number of 3 for nickel by ammonia in the aqueous phase.The uptake of SO₄^2?, NO₃^? and water by the organic phase was negligible. The uptake of ammonia was dependent upon pH and the ammonia content of the aqueous phase, and was negligible in the absence of metal.     

Luminescence properties of a single-host phosphor Bal.8-wSrwLi0.4SiO4： cea＋,Eu2＋,Mn2＋ for WLED

In order to obtain a single-host-white-light phosphor,a series of Ba1.8-w-x-y-zSrwLi0.4-xCexEuyMnzSiO4(BSLS:Ce3+,Eu2+,Mn2+)powder samples were synthesized via high temperature solid-state reaction.The structure and photoluminescence properties were investigated.Under ultraviolet excitation,the emission spectra contained three bands:the 370-470 nm blue band,the 470-570 nm green band and the 570-700 nm red band,which arose from the 5d→4f transitions of Ce3+ and Eu2+,and the 4T1→6A1 transition of Mn2+,respectively.The excitation spectra of the emissions of Ce3+ and Mn2+ ions showed the energy transfer from Ce3+ to Mn2+.White light emission was obtained from the tri-doped samples of appropriate doping concentration under 310-360 nm excitation.     

Photoluminescent properties of Ca2RE8（SiO4）6O2：A （RE=Y,Gd; A=Pb^2＋, Mn^2＋） phosphor films prepared by sol-gel process

Ca2RE8（SiO4）6O2：A （RE=Y, Gd; A=Pb^2＋, Mn^2＋） phosphor fdms were dip-coated on quartz glass substmtes through the sol-gel process. X-ray diffraction （XRD）, photoluminescence （PL） spectra as well as lifetimes were used to characterize the resulting films. Under short wavelength UV excitation, the film showed a red emission with medium intensity. The decay curve of Mn^2＋ luminescence in Ca2Gd8（SiO4）6O2：Pb Mn film could be fitted into a single exponential function. The lifetime of Mn^2＋ was 10.21 ms in Ca2Gd8（SiO4）6O2.     

Comparative study of dewatering characteristics of metal precipitates generated during treatment of monometallic solutions

The sludge dewatering properties (settling, filtration and centrifugation) of metal precipitates generated during treatment of monometallic solutions (0.020 mol/L) have been evaluated in this research. The precipitation tests carried out on 15 different metals gave metal removal yields generally similar to those predicted by MINEQL+ software, with the exception that kinetic aspects should be considered during precipitation of metal sulphides and phosphates. Hydroxides precipitation at pH 10.0 was the most efficient technique for the removal of eight metallic ions (Al³⁺, Cd²⁺, Co²⁺, Fe²⁺, Fe³⁺, Mg²⁺, Mn²⁺, Ni²⁺), whereas phosphates precipitation (at pH 6.0 with an addition of 0.0133 mol PO₄^3?/L) gave highest removal yields for Ba²⁺, Ca²⁺, Cr³⁺. Sulphides precipitation (at pH 7.0 and using, 0.020 mol S^2?/L) has been found the most efficient technique only for Cu²⁺ and Sn²⁺ precipitation, whereas carbonates precipitation (at pH 8.0 and using 0.020 mol CO₃^2?/L) gave better removal yield only for Pb²⁺. Results have also shown that metal phosphates have generally better dewatering characteristics (SVI, filtration capacity, SRF, sludge solids content) than metal carbonates, sulphides and hydroxides. In fact, considering only the sludge dewatering characteristics, phosphates precipitation appears the most appropriate technique for the precipitation of many metals (Al³⁺, Ba²⁺, Cd²⁺, Co²⁺, Cr³⁺, Fe²⁺, Fe³⁺, Ni²⁺ and Zn²⁺). Metal hydroxides formation constitutes the best option for Ca²⁺, Cu²⁺, Mg²⁺ and Sn²⁺ removal, whereas precipitation of metal carbonates is particularly interesting for treatment of Mn²⁺ and Pb²⁺ containing solutions.     

Emission tunable of Mg_(0.695)Si_(0.695)Al_(1.39)O_(3.65)N_(0.35):Eu~(2+),Mn~(2+) oxynitride phosphors via energy transfer for WLEDs

A series of Eu~(2+)doped and Eu~(2+)/Mn~(2+) co-doped Mg_(0.695)Si_(0.695)Al_(1.39)O_(3.65)N_(0.35)(MSAON) phosphors were synthesized by solid-state reaction at a lower temperature of 1500℃.The crystal morphology and structure of MSAON host were characterized by SEM,TEM and XRD.The quantum yield(QY) for Eu~(2+)doped MSAON phosphors was measured as high as 62%,indicating the excellent luminous efficiency.For the Eu~(2+)/Mn~(2+)co-doped MSAON phosphor,the photoluminescence spectrum and delay curves reveal the efficient energy transfer(ET) process from Eu2+to Mn~(2+)ions.Meanwhile,the corresponding energy transfer efficiency,critical distance and mechanism are discussed in detail.Temperature-dependent emission spectrum shows the thermal and color stabilities.The emission color of MSAON:Eu~(2+),Mn~(2+)phosphors could be tuned from blue through white to red via varying the concentration of Mn~(2+) ions.White-light-emitting diodes(WLEDs) were successfully fabricated by encapsulating the phosphors in nUV LED(365 nm) devices obtaining white light with color rendering index(CRI) as high as 87.7.The results reveal that the MSAON:Eu~(2+),Mn~(2+)phosphors could have potential application in the field of n-UV WLEDs.     

Kinetics of chromium oxide reduction from a basic steelmaking slag by silicon dissolved in liquid iron

The reduction of chromium oxide from a basic steelmaking slag (45 wt pct CaO, 35 wt pct SiO₂, 10 wt pct MgO, 10 wt pct A1₂O₃) by silicon dissolved in liquid iron at steelmaking temperatures was studied to determine the rate-limiting steps. The reduction is described by the reactions: (Cr₂O₃) + Si = (SiO₂) + (CrO) + Cr [1] and 2 (CrO) +Si = (SiO₂) + 2 Cr [2] The experiments were carried out under an argon atmosphere in a vertical resistance-heated tube furnace. The slag and metal phases were held in zirconia crucibles. The course of the reactions was followed by periodically sampling the slag phase and analyzing for total chromium, divalent chromium, and iron. Results obtained by varying stirring rate, temperature, and composition defined the rate-limiting mechanism for each reaction. The rate of reduction of trivalent chromium (reaction [1] above) increases with moderate increases in stirring of the slag, and increases markedly with increases in temperature. The effects of changes in composition identified the rate-limiting step for Cr⁺³ reduction as diffusion of Cr⁺³ from the bulk slag to the slag-metal interface. The rate of reduction of divalent chromium does not vary with changes in stirring of the slag, but increases in temperature markedly increase the reaction rate. Thus, this reaction is limited by the rate of an interfacial chemical reaction. The reduction of divalent chromium is linearly dependent on concentration of divalent chromium, but is independent of silicon content of the metal phase.     

Distribution of nickel between copper-nickel and alumina saturated iron silicate slags

The solubility of nickel in slag was determined by equilibrating copper-nickel alloys with alumina-saturated iron silicate slags in an alumina crucible at 1573 K. The experiments were carried out under controlled oxygen partial pressures in the range of 10^-10 to 10^-8 atm by use of suitable CO-CO₂ gas mixtures, and at Fe/SiO₂ ratio 1.34. The results showed that nickel dissolves in slag both as Ni²⁺ (nickel oxide) and Ni‡ (nickel metal), and the relation obtained was: (Wt pct Ni in slag) = (ie33-01) The activity coefficient of nickel oxide (γ^dgNio) and distribution coefficient of nickel (A_Ni) is calculated to be 0.375 and 233.3, respectively. γ^dgNio and A_Ni are found to be independent of oxygen partial pressures. The presence of alumina increases the solubility of nickel in slags.     

Color-tunable Ca10Na(PO4)7:Ce3+/Tb3+/Mn2+ phosphor via energy transfer

A series of Ca_(10)Na(PO_4)_7:Ce~(3+)/Tb~(3+)/Mn~(2+)(CNPO:Ce~(3+)/Tb~(3+)/Mn~(2+)) phosphors with high brightness were synthesized by high-temperature solid-state method. X-ray diffraction(XRD), scanning electron microscopy(SEM), diffuse reflectance spectra(DRS), photo luminescence(PL) spectra, luminescence decay curves and thermally stability were performed to characterize the as-prepared samples. For Ce~(3+)-doped samples, an intense and broad band emission is present under 265 nm excitation. When Ce~(3+) and Tb~(3+)are codoped, energy transfer(ET) process from Ce3+ to Tb3+ is demonstrated with electric dipole-dipole interaction. The internal and external quantum efficiencies(QEs) of CNPO:0.15 Ce~(3+), 0.04 Tb~(3+), 0.005 Mn~(2+)are measured to 76.79% and 54.11% under 265 nm excitation and temperature-dependent PL intensity can remain 51.78% at 150 ℃ of its initial intensity at 25 ℃. It is indicated that single-phased white lightemitting CNPO:Ce~(3+)/Tb~(3+)/Mn~(2+) phosphor can serve as a promising phosphor for illumination devices.     

Enthalpies of formation of liquid (copper + manganese) alloys

The enthalpies of formation of liquid (Cu + Mn) alloys were measured in the isoperibolic heat-flux calorimeter at 1573 K in the entire range of compositions. The integral molar enthalpy of mixing was found to be negative in the range of molar fractions 0 < x _Mn < 0.31, with ΔH(min) = −0.69 ± 0.27 kJ mol⁻¹ at x _Mn = 0.12, and positive in the range 0.31 < x _Mn < 1, with ΔH(max) = 3.67 ± 0.36 kJ mol⁻¹ at x _Mn = 0.75. Limiting partial molar enthalpies of manganese and copper were calculated as = −18.0 ± 6.6 kJ mol⁻¹ and = 29.1 ± 4.9 kJ mol⁻¹, respectively. The results are discussed in comparison with the thermodynamic data available in the literature and the equilibrium phase diagram.     

Tunable luminescence in co-doped Zn3Al2Ge2O10:Cr3+ by controlling crystal field splitting and nephelauxetic effect

Ce³⁺/Dy³⁺/Tb³⁺/Eu³⁺/Mn²⁺ and Cr³⁺ ions co-doped Zn₃Al₂Ge₂O₁₀ phosphor were prepared by a high-temperature solid-state method. X-ray diffraction patterns prove the cubic phase structure of prepared Zn₃Al₂Ge₂O₁₀ phosphor. Emission, excitation spectra and decay curves confirm the tunable luminescence. Different degrees of the decrease of emission FWHM in Zn₃Al₂Ge₂O₁₀:0.02Cr³⁺,RE (RE = Ce³⁺, Dy³⁺, Tb³⁺, Eu³⁺) and Zn₃Al₂Ge₂O₁₀:0.02Cr³⁺,Mn²⁺ are observed. The reason of variable FWHM is the effect of crystal field splitting and nephelauxetic effect, and the nephelauxetic effect is dominant. Therefore, the emission FWHM decreases with the increasing concentration of Mn²⁺/Tb³⁺/Eu³⁺ in Zn₃Al₂Ge₂O₁₀:0.02Cr³⁺, and for Zn₃Al₂Ge₂O₁₀:0.02Cr³⁺,Ce³⁺ and Zn₃Al₂Ge₂O₁₀:0.02Cr³⁺,Dy³⁺, it is a constant. The variation of Zn₃Al₂Ge₂O₁₀:0.02Cr³⁺,Tb³⁺ is more obvious than that of Zn₃Al₂Ge₂O₁₀:0.02Cr³⁺,Eu³⁺, because Tb³⁺ ion has smaller electronegativity. Thus, the tunable luminescence of Cr³⁺ can be realized by co-doping different ions. And these phosphors have potential applications in light-emitting diodes for plant growth.     

Effect of SiO2 introduction on luminescence properties of LuAG:Mn2+ phosphors

Mn²⁺doped LuAG phosphors with different contents of Si⁴⁺ions were synthesized via the solid-state reaction method and the effects of Si⁴⁺doping on the crystal structure and luminescence properties of phosphors were studied.XRD patterns of all phosphors exhibit a pure phase but with different extents of deviations.Owing to the 4 T1→6 A1 transition of Mn²⁺,the LuAG:Mn²⁺,Si⁴⁺phosphors exhibit a broad emission band with an emission peak at 582 nm.Moreover,the introduction of Si⁴⁺not only improves the emission intensity but also induces a red-shift with the emission peak from 582 to 612 nm and the spectra broadening with the full width at half maximum value from 64 to 74 nm,which results from the decrease of bond length between O2-anions and Mn²⁺cations and the re-absorption of Mn²⁺-Mn²⁺pairs.Suitable content of Si⁴⁺replacement can weaken thermal quenching of Mn²⁺.Thus,via regulating the content of Si,the Mn²⁺,Si⁴⁺co-doped LuAG phosphor with low correlated color temperature is a candidate for warm wLEDs.     

Enhanced luminescence performances of Mn~(4+)-activated Sr_4Al_(14)O_(25) red phosphors by doping with Sc~(3+) ions

A series of non-rare earth Mn⁴⁺-activated strontium aluminate phosphors Sr₄Al₁₄O₂₅:Mn⁴⁺co-doped with Sc³⁺ions were successfully synthesized by a high-temperature solid-state reaction method.XRD result reveals that there is no introduction of additional phase but expansion of lattice with incorporation of Sc34 ions.Excitation and emission spectrum measurement shows that the synthesized phosphors can be efficiently excited by near-ultraviolet and blue light,and a deep red emission centered at 652 nm with a narrow full width at half maximum(FWHM)can be obtained,which is attributed to the transition²E→⁴A₂of Mn⁴⁺ions.In addition,the crystal field strength parameter(Dq)and Racah parameters(B,C)and energies of states were calculated based on experimental data.Moreover,the luminous intensity of Sr₄Al_14-xSCxO₂₅:Mn⁴⁺is enhanced and increased by 60%compared with Mn⁴⁺single incorporated sample at x=0.06.A phenomenon of redshift is observed in the excitation spectrum and discussed systematically.Finally,the mechanism of the positive effects with Sc³⁺ions incorporated into lattice is discussed in detail.All the results suggest that the Sr₄Al_13.94Sc_0.06O₂₅:Mn⁴⁺phosphor will become one of the great candidates for backlight of LCD.