The luminescent enhancement of LaPO4:Ce3+,Tb3+ nano phosphors by radial aggregation

The rare earth nano phosphors can meet the challenging demand for new functional devices but their luminescence is always poor. Here we report on a simple method to prepare uniform LaPO₄:Ce³⁺,Tb³⁺ sphere-like nano aggregates from the precipitated nano phosphor crystallites without using any additive. The spontaneous aggregation is induced and controlled only by the suspension pH conditions. It is found that the 100 nm spherical aggregates can significantly improve the green emissions of the LaPO₄:Ce³⁺,Tb³⁺ nano particles. The intensity of the aggregates can be about 10 times as that of the 80 nm-sized individual ones. This study may provide a useful yet convenient strategy in the improvement and application of nano phosphors.     

Luminescence properties and energy transfer of co-doped Ba<Subscript>3</Subscript>GdNa(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>F:Ce<Superscript>3+</Superscript>,Tb<Superscript>3+</Superscript> green-emitting phosphors

Phase pure Ce³⁺ and Tb³⁺ singly doped and Ce³⁺/Tb³⁺ co-doped Ba₃GdNa(PO₄)₃F samples have been synthesized via the high temperature solid-state reaction. The crystal structures, photoluminescence properties, fluorescence lifetimes, thermal properties and energy transfer of Ba₃GdNa(PO₄)₃F:Ce³⁺,Tb³⁺ were systematically investigated. Rietveld structure refinement indicates that Ba₃GdNa(PO₄)₃F crystallizes in a hexagonal crystal system with the space group P-6. For the co-doped Ba₃GdNa(PO₄)₃F:Ce³⁺,Tb³⁺ samples, the emission color can be tuned from blue to green by varying the doping concentration of the Tb³⁺ ions. The intense green emission was realized in the Ba₃GdNa(PO₄)₃F:Ce³⁺,Tb³⁺ phosphors on the basis of the highly efficient energy transfer from Ce³⁺ to Tb³⁺. Also the energy transfer mechanism has been confirmed to be quadrupole–quadrupole interaction, which can be validated via the agreement of critical distances obtained from the concentration quenching (13.84 Å). These results show that the developed phosphors may possess potential applications in near-ultraviolet pumped white light-emitting diodes.     

Synthesis,tunable luminescence and thermal stability of Mg<Subscript>2</Subscript>Al<Subscript>4</Subscript>Si<Subscript>5</Subscript>O<Subscript>18</Subscript>:Ce<Superscript>3+</Superscript>/Mn<Superscript>2+</Superscript> phosphors

Ce³⁺/Mn²⁺ singly doped and codoped Mg₂Al₄Si₅O₁₈ phosphors were synthesized by a solid state reaction. The phase, luminescent properties and thermal stability of the synthesized phosphors were investigated. Ce³⁺ and Mn²⁺ singly doped Mg₂Al₄Si₅O₁₈ phosphors show emission bands locating in blue and yellow–red regions, respectively. In Ce³⁺ and Mn²⁺ codoped Mg₂Al₄Si₅O₁₈, tunable luminescence was obtained because of the energy transfer from Ce³⁺ to Mn²⁺. In Mg₂Al₄Si₅O₁₈:Ce³⁺/Mn²⁺ phosphors with a fixed Ce³⁺ concentration, energy transfer efficiency increases with the increasing Mn²⁺ concentration, which is confirmed by the continually decreasing intensity and shortening decay time of Ce³⁺ emission. Moreover, the luminescent properties and thermal stability provide a great significance on the applications in the field of light emitting diodes.     

Synthesis and luminescent characterization of YAl<Subscript>3</Subscript>(BO<Subscript>3</Subscript>)<Subscript>4</Subscript>:Tb<Superscript>3+</Superscript> phosphors

YAl₃(BO₃)₄:Tb³⁺ phosphors were fabricated by the sol–gel method. The phosphor showed prominent luminescence in green due to the magnetic dipole transition of ⁵D₄–⁷F₅. Structural characterization of the luminescent material was carried out with X-ray powder diffraction (XRD) analysis. Luminescence properties were analyzed by measuring the excitation and photoluminescence spectra. Photoluminescence measurements indicated that the phosphor exhibited bright green emission at about 541 nm under UV excitation. It is shown that the 11% of doping concentration of Tb³⁺ ions in YAl₃(BO₃)₄:Tb³⁺ phosphors is optimum.     

Influence of Mg<Superscript>2+</Superscript>/Ga<Superscript>3+</Superscript> doping on luminescence of Y<Subscript>3</Subscript>Al<Subscript>5</Subscript>O<Subscript>12</Subscript>:Ce<Superscript>3+</Superscript> phosphors

Mg²⁺/Ga³⁺ doped Y₃Al₅O₁₂:Ce³⁺ phosphors were synthesized through a solid state reaction. The phase and luminescent of the synthesized phosphors were investigated. For Ga³⁺ codoped Y_2.96Ce_0.04Al_(5?x)Ga_xO₁₂ phosphors, the emission intensity increases with the increase of Ga³⁺ concentration up to Y_2.96Ce_0.04Al_4.80Ga_0.20O₁₂ and then decreases with a further increase of Ga³⁺ concentration, but the emission peak shifts to shorter wavelength continuously in the Ga³⁺ doping concentration range of 0.05–0.25. For Mg²⁺/Ga³⁺ codoped Y_2.96Ce_0.04Al_(4.8?y)Ga_0.20Mg_yO₁₂ phosphors, the emission intensity decreases and the emission peak shifts to longer wavelength continuously in the Mg²⁺ doping concentration range of 0.02–0.12. The emission spectra of Y_2.96Ce_0.04Al_(4.8?y)Ga_0.20Mg_yO₁₂ phosphors demonstrate that the codoped Mg²⁺/Ga³⁺ ions not only induce the enhancement of Y_2.96Ce_0.04Al₅O₁₂ emission intensity but also lead to the red shift of Y_2.96Ce_0.04Al₅O₁₂ emission peak. The decay lifetimes decrease in Mg²⁺/Ga³⁺ codoped Y_2.96Ce_0.04Al₅O₁₂ phosphors due to defects formed by substitutions of Y³⁺ by Mg²⁺/Ga³⁺.     

Synthesis and luminescence properties of a novel UV-emitting phosphor Sr<Subscript>3</Subscript>P<Subscript>4</Subscript>O<Subscript>13</Subscript>:Ce<Superscript>3+</Superscript>

The ultraviolet (UV)-emitting Sr₃P₄O₁₃:Ce³⁺ phosphors were synthesized via the solid-state reaction method, and their structural, morphological and luminescence properties were characterized by X-ray diffraction analysis, scanning electron microscopy, photoluminescence spectroscopy. The obtained results indicate that these phosphors can be effectively excited by short-wavelength ultraviolet (<300 nm), and exhibit long-wavelength ultraviolet (300–380 nm) emission with nanosecond-level fluorescence lifetime corresponding to the parity-allowed 5d–4f transitions of Ce³⁺. The concentration-quenching phenomenon of Ce³⁺ in Sr₃P₄O₁₃ host was also studied, in which the critical energy transfer distance between Ce³⁺ ions and concentration quenching mechanism were determined.     

Solid state synthesis,microstructure and photoluminescence of Eu<Superscript>3+</Superscript> and Tb<Superscript>3+</Superscript> activated strontium tungstate

The Eu³⁺ and Tb³⁺ ions activated SrWO₄ phosphors have been synthesized by solid state method. The crystal structures and morphologies of the products are characterized by Powders X-ray Diffraction (XRD) and scanning electronic microscopy (SEM). The results indicated that both SrWO₄:Eu³⁺ and SrWO₄:Tb³⁺ phosphors belong to tetragonal phase, and the particles of the phosphors become aggregate with the increase of calcinations temperature. Analyzed by luminescent spectra, the dominant emission of Eu³⁺ in SrWO_4, which is the typical hypersensitive transition ⁵D₀ → ⁷F₂ (613 nm), and the green emission (⁵D₄ → ⁷F₅) intensity of Tb³⁺ in SrWO₄:Tb³⁺ is also dominant. The reaction temperature had obvious influence on the luminescent properties. The intensity reached the strongest when it is sintered at 900 °C. Therefore, we can try to select the right temperature in order to obtain the ideal product.     

Persistent luminescence of Zn<Subscript>2</Subscript>GeO<Subscript>4</Subscript>:Mn<Superscript>2+</Superscript>/Pr<Superscript>3+</Superscript> phosphors

Zn₂GeO₄, Zn₂GeO₄:Mn²⁺, Zn₂GeO₄:Pr³⁺ and Zn₂GeO₄:Mn²⁺/Pr³⁺ phosphors were fabricated by a solid state reaction. The phase and luminescent properties of the fabricated phosphors were investigated. The XRD patterns show that all of the fabricated phosphors have an orthorhombic structure. The fabricated Zn₂GeO₄ shows an emission band in the range of 350–550 nm. The fabricated Zn₂GeO₄:Mn²⁺ and Zn₂GeO₄:Pr³⁺ phosphors show emission bands corresponding to Mn²⁺ and Pr³⁺ ions, respectively. The fabricated Zn₂GeO₄:Mn²⁺/Pr³⁺ phosphor shows the emission band results from Mn²⁺ and the codoped Pr³⁺ enhances the emission intensity of Mn²⁺. Moreover, Zn₂GeO₄:Mn²⁺/Pr³⁺ phosphor exhibits longer decay time than that of Zn₂GeO₄:Mn²⁺. The higher intensity and longer lifetime of Mn²⁺ emission are induced by the energy transfer from Pr³⁺ of various vacancies to Mn²⁺ in Zn₂GeO₄:Mn²⁺/Pr³⁺ phosphors.     

Hydrothermal synthesis and luminescence properties of core-shell-structured PS@SrCO<Subscript>3</Subscript>:Tb<Superscript>3+</Superscript> spherical particles

Nanocrystalline SrCO₃:Tb³⁺ phosphor layers were coated on monodisperse and spherical polystyrene particles by a typical hydrothermal synthesis without further annealing treatment, resulting in the formation of core-shell-structured polystyrene@SrCO₃:Tb³⁺ particles. X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, photoluminescence, as well as lifetimes were employed to characterize the resulting composite particles. Under ultraviolet excitation, the polystyrene@SrCO₃:Tb³⁺ phosphors show the characteristic ⁵D₄–⁷F _J (J = 6, 5, 4, 3) emission lines with green emission ⁵D₄–⁷F₅ (544 nm) as the most prominent group. The obtained core-shell phosphors are potentially applied in fluorescent lamps.     

Synthesis,structural, photoluminescence and mechanoluminescence properties of Tb<Superscript>3+</Superscript>: Ca<Subscript>2</Subscript>Gd<Subscript>2</Subscript>W<Subscript>3</Subscript>O<Subscript>14</Subscript> novel green nanophosphors

Novel green nanophosphors Ca₂Gd₂W₃O₁₄: Tb³⁺ were synthesized by solid state reaction method. From the X-ray diffraction profiles it is observed that Tb³⁺: Ca₂Gd₂W₃O₁₄ phosphors were crystallized in the form of tetragonal structure. The scanning electron microscopy (SEM) image shows that the particle size is at around 300 nm. In addition to these the prepared powder phosphors were also examined by the energy dispersive X-ray analysis (EDAX), Fourier transform infrared spectroscopy (FTIR), photoluminescence (PL) and mechanoluminescence (ML) spectra. Emission spectra of Tb³⁺: Ca₂Gd₂W₃O₁₄ nanophosphors have shown bright green emission at 545 nm (⁵D₄ → ⁷F₅) with an excitation wavelength λ_exci = 374 nm (⁷F₆ → ⁵G₆). ML spectra shows the radiation effect on the Ca₂Gd₂W₃O₁₄: Tb³⁺ nanophosphors and from that it was observed that these phosphors are very less sensitive for lower exposure.     

Hydrothermal synthesis and photoluminescence properties of Y<Subscript>2</Subscript>Zr<Subscript>2</Subscript>O<Subscript>7</Subscript>:Tb<Superscript>3+</Superscript> phosphors

This article presents the synthesis and photoluminescence (PL) properties of Y₂Zr₂O₇:Tb³⁺. The Tb³⁺-doped Y₂Zr₂O₇ zirconates were successfully synthesized by a hydrothermal process at 200 °C for 20 h. X-ray diffractometer (XRD) patterns revealed that all of the products were phase-pure with the fluorite structure. PL study showed that the Y₂Zr₂O₇:Tb³⁺ phosphors exhibited obvious PL emission peaks which located at 490, 545, 585, and 623 nm; the dominant emission located at 545 nm is assigned to ⁵D₄ → ⁷F₅ transition. Furthermore, Tb³⁺-doping concentration strongly affected the PL properties, and the quenching concentration is 5 at.%.     

Synthesis and photoluminescence study of narrow-band UVB-emitting LiSr<Subscript>4</Subscript>(BO<Subscript>3</Subscript>)<Subscript>3</Subscript>:Gd<Superscript>3+</Superscript>, Pr<Superscript>3+</Superscript> phosphor

A series of Pr³⁺, Gd³⁺ and Pr³⁺–Gd³⁺-doped inorganic borate phosphors LiSr₄(BO₃)₃ were successfully synthesized by a modified solid-state diffusion method. The crystal structures and the phase purities of samples were characterized by powder X-ray diffraction. Surface morphology of the sample was studied by scanning electronic microscopy (SEM). The optimal concentrations of dopant Gd³⁺ ions in compound LiSr₄(BO₃)₃ were determined through the measurements of photoluminescence (PL) spectra of phosphors. Gd³⁺-doped phosphors LiSr₄(BO₃)₃ show strong band absorption in UV spectral region and narrow-band UVB emission under the excitation of 276 nm was only due to ⁶P _J → ⁸S_7/2 transition of Gd³⁺ ions. The effect of Pr³⁺ ion on excitation of LiSr₄(BO₃)₃:Gd³⁺ was also studied. The excitation of LiSr₄(BO₃)₃:Gd³⁺, Pr³⁺ gives a broad-band spectra, which show very good overlap with the Hg 253.7 nm line. The photoluminescence spectra of LiSr₄(BO₃)₃ with different doping concentrations Pr³⁺ and keeping the concentration of Gd³⁺ constant at 0.03 mol have also been studied. The emission intensity of LiSr₄(BO₃)₃:Pr³⁺–Gd³⁺ phosphors increases with increasing Pr³⁺ doping concentration and reaches a maximum at 0.01 mol. From the photoluminescence study of LiSr₄(BO₃)₃:Gd³⁺, Pr³⁺ we conclude that there was efficient energy transfer from Pr³⁺→ Gd³⁺ ions in LiSr_4?x?y Pr _x Gd _y (BO₃)₃ phosphors.     

Influence of Mn<Superscript>2+</Superscript> on the up-conversion emission performance of Mn<Superscript>2+</Superscript>, Yb<Superscript>3+</Superscript>, Er<Superscript>3+</Superscript>: ZnWO<Subscript>4</Subscript> green phosphors

The Mn²⁺, Yb³⁺, Er³⁺: ZnWO₄ green phosphors are synthesized successfully through the high temperature solid state reaction method. The micro-structure and morphology have been investigated by means of XRD and EDS. The doped concentrations of Mn²⁺, Yb³⁺, Er³⁺ are measured by ICP. The absorption spectra and emission spectra with different doped concentrations of Mn²⁺ are presented to reveal the influence of Mn²⁺ on the green up-conversion performance. Excited with 970 nm LED, the up-conversion emission peak at 547 nm is obtained and the CIE spectra as well as the green light photo are also presented. The results indicate that the Mn²⁺ ions play the role of the luminescence adjustment in the up-conversion process, which can improve the up-conversion green emission intensity effectively. The luminescence adjustment mechanism of Mn²⁺ ions in Mn²⁺, Yb³⁺, Er³⁺: ZnWO₄ green phosphors has been discussed. The crystal parameters of Dq, B and C are calculated to evaluate the energy level split effect.     

Roles of doping ions in persistent luminescence of SrAl<Subscript>2</Subscript>O<Subscript>4</Subscript>:Eu<Superscript>2+</Superscript>, RE<Superscript>3+</Superscript> phosphors

The polycrystalline Eu²⁺ and RE³⁺ co-doped strontium aluminates SrAl₂O₄:Eu²⁺, RE³⁺ were prepared by solid state reactions. The UV-excited photoluminescence, persistent luminescence and thermo-luminescence of the SrAl₂O₄:Eu²⁺, RE³⁺ phosphors with different composition and doping ions were studied and compared. The results showed that the doped Eu²⁺ ion in SrAl₂O₄:Eu²⁺, Dy³⁺ phosphors works as not only the UV-excited luminescent center but also the persistent luminescent center. The doped Dy³⁺ ion can hardly yield any luminescence under UV-excitation, but can form a electron trap with appropriate depth and greatly enhance the persistent luminescence and thermo-luminescence of SrAl₂O₄:Eu²⁺. Different co-doping RE³⁺ ions showed different effects on persistent luminescence. Only the RE³⁺ ion (e.g. Dy³⁺, Nd³⁺), which has a suitable optical electro-negativity, can form the appropriate electron trap and greatly improve the persistent luminescence of SrAl₂O₄:Eu²⁺. Based on above observations, a persistent luminescence mechanism, electron transfer model, was proposed and illustrated.     

Synthesis and luminescence properties of a novel Eu<Superscript>3+</Superscript>, Tb<Superscript>3+</Superscript> co-doped Al<Subscript>18</Subscript>B<Subscript>4</Subscript>O<Subscript>33</Subscript> whiskers by a gel nano-coating method

Al₁₈B₄O₃₃:Eu³⁺, Tb³⁺ whiskers have been successfully prepared by a simple gel nano-coating method using aluminum isopropoxide as the starting materials. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), photoluminescence (PL), and thermogravimetric analysis (TGA) were used characterize the samples. The results show coexistence of the crystal phase Al₁₈B₄O₃₃, amorphous phase, and Eu³⁺, Tb³⁺ ions of the samples with initial addition Al/B ratios from 3 to 1 are incorporated into the amorphous phase. The Al₁₈B₄O₃₃:Eu³⁺, Tb³⁺ whiskers are very straight with an average diameter of 600 nm and lengths ranging from 5 to 10 μm. Under ultraviolet excitation at 365 nm, samples show mainly exhibit the characteristic emission of Eu³⁺ corresponding to \( ^{ 5} {\text{D}}_{ 0} \to {\text{F}}_{ 1 , 2} \) transitions due to an efficient energy transfer occurs from Tb³⁺ to Eu³⁺.     

Tunable luminescence of SrLaMgTaO<Subscript>6</Subscript>:Sm<Superscript>3+</Superscript> phosphors due to energy transfer from TaO<Subscript>6</Subscript> group to Sm<Superscript>3+</Superscript> ion

A series of SrLaMgTaO₆:Sm³⁺ phosphors were synthesized through a solid state reaction. The phase, microstructure and luminescent properties of the synthesized phosphors were investigated through techniques of XRD, SEM and spectrophotometer. The XRD patterns show that the synthesized phosphors have the same phase structure. The SEM images show that the synthesized phosphors are microcrystallines in the range of 1.2–3.4 µm. SrLaMgTaO₆:Sm³⁺ phosphors present emission bands originating from TaO₆ group and Sm³⁺ ions. The critical concentration of Sm³⁺ in SrLaMgTaO₆ is found to be 7 mol%. Due to energy transfer from TaO₆ group to Sm³⁺, tunable luminescence is obtained by changing Sm³⁺ doping concentration.     

Sr<Subscript>3</Subscript>GdLi(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>F: Sm<Superscript>3+</Superscript> phosphor: preparation and luminescence properties evaluation

A series of Sr₃Gd_1?xLi(PO₄)₃F: xSm³⁺ (x?=?0.02, 0.04, 0.06, 0.08) phosphors were synthesized by a high-temperature solid state method. The Sm³⁺ activated Sr₃GdLi(PO₄)₃F phosphors can be efficiently excited by the wavelengths in the range from 350 to 450 nm, which matches perfectly with that of the commercial near-UV LED chips. The optimal doping concentration of Sr₃Gd_1?xLi(PO₄)₃F: xSm³⁺ phosphors was determined to be x?=?0.04, corresponding to the quantum efficiency of 2.23%, and the CIE chromaticity coordinates (x?=?0.5172, y?=?0.4641). The concentration quenching mechanism of Sm³⁺ in Sr₃GdLi(PO₄)₃F host is mainly attributed to the dipole–dipole interaction, which was confirmed by the fluorescent lifetimes. The effect of temperature on the photoluminescence property of Sr₃GdLi(PO₄)₃F: Sm³⁺ was investigated. 90% of the intensity is preserved at 150 °C. In addition, a white light emitting diode (WLED) lamp was fabricated by a 405 nm n-UV LED chip coated with Sr₃Gd_0.96Li(PO₄)₃F:0.04Sm³⁺ phosphor and commercial yellow phosphor (YAG: Ce³⁺) of a certain mass ratio. The present work indicates that the Sr₃GdLi(PO₄)₃F: Sm³⁺ orange–red-emitting phosphors tend to be potential application in n-UV WLED.     

Tunable luminescence properties and energy transfer of single-phase Ca<Subscript>4</Subscript>(PO<Subscript>4</Subscript>)<Subscript>2</Subscript>O: Dy<Superscript>3+</Superscript>, Eu<Superscript>2+</Superscript> multi-color phosphors for warm white light

The novel Ca_4?x(PO₄)₂O: xDy³⁺ and Ca_4?x?y(PO₄)₂O: xDy³⁺, yEu²⁺ multi-color phosphors were synthesized by traditional solid-state reaction. The crystal structure, particle morphology, photoluminescence properties and energy transfer process were investigated in detail. The X-ray diffraction (XRD) results demonstrate that the products showed pure monoclinic phase of Ca₄(PO₄)₂O when x < 0.1. The scanning electron microscopy (SEM) indicated that the phosphors were grain-like morphologies with diameters of ~ 3.7–7.0 μm. Under excitation of 345 nm, Dy³⁺-doped Ca₄(PO₄)₂O phosphors showed multi-color emission bands at 410, 481 and 580 nm originated from oxygen vacancies and Dy³⁺. Interestingly, Ca₄(PO₄)₂O: Dy³⁺, Eu²⁺ phosphors exhibited blue emission band at 481 nm and broad emission band from 530 to 670 nm covering green to red regions. The energy transfer process from Dy³⁺ to Eu²⁺ was observed for the co-doped samples, and the energy transfer efficiency reached to 60% when Eu²⁺ molar concentration was 8%. In particular, warm/cool/day white light with adjustable CCT (2800–6700 K) and high CRI (R_a > 85) can be obtained by changing the Eu²⁺ co-doping contents in Ca₄(PO₄)₂O: Dy³⁺, Eu²⁺ phosphors. The optimized Ca_3.952(PO₄)₂O: 0.04Dy³⁺, 0.008Eu²⁺ phosphor can achieve the typical white light with CCT of 4735 K and CRI of 87.     

The comparison: photoluminescence and afterglow behavior in CaSnO<Subscript>3</Subscript>:Dy<Superscript>3+</Superscript> and Ca<Subscript>2</Subscript>SnO<Subscript>4</Subscript>:Dy<Superscript>3+</Superscript> phosphors

This paper reports the comparison of photoluminescence and afterglow behavior of Dy³⁺ in CaSnO₃ and Ca₂SnO₄ phosphors. The samples containing CaSnO₃ and Ca₂SnO₄ were prepared via solid-state reaction. The properties have been characterized and analyzed by utilizing X-ray diffraction (XRD), photoluminescence spectroscope (PLS), X-ray photoelectron spectroscopy (XPS), afterglow spectroscopy (AS) and thermal luminescence spectroscope (TLS). The emission spectra revealed that CaSnO₃:Dy³⁺ and Ca₂SnO₄:Dy³⁺ phosphors showed different photoluminescence. The Ca₂SnO₄:Dy³⁺ phosphor showed a typical ⁴F_9/2 to ⁶H_j energy transition of Dy³⁺ ions, with three significant emissions centering around 482, 572 and 670 nm. However, the CaSnO₃:Dy³⁺ phosphor revealed a broad T₁ → S₀ transitions of Sn²⁺ ions. The XPS demonstrate the existence of Sn²⁺ ions in CaSnO₃ phosphor caused by the doping of Dy³⁺ ions. Both the CaSnO₃:Dy³⁺ and Ca₂SnO₄:Dy³⁺ phosphors showed a typical triple-exponential afterglow when the UV source switched off. Thermal simulated luminescence study indicated that the persistent afterglow of CaSnO₃:Dy³⁺ and Ca₂SnO₄:Dy³⁺ phosphors was generated by the suitable electron or hole traps which were resulted from the doping the calcium stannate host with rare-earth ions (Dy³⁺).     

Hydrothermal synthesis of NaLa(WO<Subscript>4</Subscript>)<Subscript>2</Subscript>:Eu<Superscript>3+</Superscript> octahedrons and tunable luminescence by changing Eu<Superscript>3+</Superscript> concentration and excitation wavelength

NaLa(WO₄)₂:Eu³⁺ phosphors with different Eu³⁺ concentrations have been synthesized by a hydrothermal method. The phase is confirmed by XRD analysis, which shows a pure-phase NaLa(WO₄)₂ XRD pattern for all of NaLa(WO₄)₂:Eu³⁺ phosphors. The SEM and TEM images indicate that all of NaLa(WO₄)₂:Eu³⁺ phosphors have a octahedral morphology. These suggest that the Eu³⁺ doping has no influence on the structure and growth of NaLa(WO₄)₄ particles. By monitoring the emission of Eu³⁺ at 615 nm, NaLa(WO₄)₂:Eu³⁺ phosphors show excitation bands originating from both host and Eu³⁺ ions. Under the excitation at 271 nm corresponding to WO₄ ^2? groups, emission bands coming from the ¹A₁ → ³T₁ transition with the WO₄ ^2? groups and the ⁵D₀ → ⁷F_j (j = 0, 1, 2, 3 and 4) transitions of Eu³⁺ are observed. The emission intensity relating to WO₄ ^2? groups decreases with increasing Eu³⁺ concentration. But emission intensities of Eu³⁺ increase firstly and then decreases because of concentration quenching effect. Under the excitation at 395 nm corresponding to ⁷F₀ → ⁵L₆ transition of Eu³⁺, only characteristic Eu³⁺ emission bands can be observed. The results of this work suggest that tunable luminescence can be obtained for Eu³⁺ doped NaLa(WO₄)₂ phosphors by changing Eu³⁺ concentration and excitation wavelength.