Search

Li5La3Ta2O12:Mn4+ (LLTO:Mn4+) phosphors are prepared in air via high‐temperature solid‐state method and investigated for their crystal structures and luminescence properties. LLTO:Mn4+ phosphor under excitation at 314 nm shows deep‐red emission peaking at 714 nm due to the 2E→4A2 transition of Mn4+ ion. The excitation bands in the range 220 ‐ 570 nm are attributed to the Mn4+ ‐ O2‐ charge‐transfer band and the 4A2g→4T1g, 2T2g, and 4T2g transitions of Mn4+, respectively. The optimal Mn4+ ion concentration is ~0.4 mol%. The concentration quenching mechanism in LLTO:Mn4+ phosphor is electric dipole‐dipole interaction. The luminous mechanism and temperature quenching phenomenon are explained by the Tanabe‐Sugano energy level diagram and the configurational coordinate diagram of Mn4+ in the octahedron, respectively. The experimental results indicate that LLTO:Mn4+ phosphor has a potential application prospect as candidate of deep‐red component in light‐emitting diode (LED) lighting. [ABSTRACT FROM AUTHOR]

A deep-red-emitting Na1.57Zn0.57Al10.43O17:Mn4+ (NZAO:Mn4+) phosphor has been synthesized by high-temperature solid-state reaction method in air. X-ray diffraction patterns confirmed only one pure phase (NZAO) in the NZAO:Mn4+ phosphor. The excitation spectrum of NZAO:Mn4+ phosphor monitored at 695 nm covered the region from 220 nm to 600 nm. Under excitation at 300 nm, NZAO:Mn4+ phosphor showed deep-red emission due to the 2E → 4A2 transition of Mn4+ ion with the lattice vibrations. In NZAO:Mn4+ phosphor, the optimal Mn4+ content is ~ 1.0%. The lifetime of NZAO:1%Mn4+ phosphor is ~ 0.47 ms. The effect of the crystal field on the luminescence properties of Mn4+ ion and the luminous mechanism are explained based on the Tanabe-Sugano diagram of Mn4+ ion in an octahedral symmetry environment. These experimental results will be helpful for research into the basis of the luminescence properties of other Mn4+-doped materials. [ABSTRACT FROM AUTHOR]

NaCa 2 Mg 2 V 3 O 12 :Sm3+ phosphors are successfully prepared in air via solid-state reaction method. The crystal structures, concentration-dependent emission spectra, decay curves, and luminescence properties are investigated. The prepared samples have only a single phase (NaCa 2 Mg 2 V 3 O 12). The excitation spectrum of host (NaCa 2 Mg 2 V 3 O 12) monitored at 510 nm is observed in the region from 210 nm to 400 nm. The host (NaCa 2 Mg 2 V 3 O 12) with excitation at 340 nm shows a strong broadband green emission with a maximum at 510 nm in the range of 400–800 nm. The excitation spectrum of NaCa 2 Mg 2 V 3 O 12 :Sm3+ phosphor monitored at 618 nm is shown in the region from 210 nm to 550 nm, which includes many absorption peaks. NaCa 2 Mg 2 V 3 O 12 :Sm3+ phosphor with excitation at 340 nm displays the tunable emission color in the region from green to yellow light with changing Sm3+ concentration, however, that with excitation at 406 nm only emits red light. The optimual Sm3+ concentration is about 4 mol% in NaCa 2 Mg 2 V 3 O 12 :Sm3+ phosphor. The lifetime of NaCa 2 Mg 2 V 3 O 12 :Sm3+ phosphor decreases from 929.16 μs to 832.11 μs with increasing Sm3+ concentration. The luminous mechanism of NaCa 2 Mg 2 V 3 O 12 :Sm3+ phosphor is explained by the configurational coordinate diagram of VO 4 3− and energy level diagram of Sm3+ ion. The experimental results are beneficial to the research of other Sm3+-doped luminescence materials. [ABSTRACT FROM AUTHOR]

A double perovskite Sr 2 ZnMoO 6 :Mn 4+ (SZM:Mn 4+ ) phosphor is synthesized by high-temperature solid-state reaction method in air. Emission band peaking at ∼705 nm of SZM:Mn 4+ phosphor in the range of 650–790 nm is attributed to the 2 E → 4 A 2 transition of Mn 4+ ion with activated different lattice vibration modes. Three excitation bands in the range of 210–610 nm are assigned to the O 2− → Mn 4+ charge transfer and the 4 A 2 → ( 4 T 1 , 2 T 2 , and 4 T 2 ) transition of Mn 4+ ion. The optimal Mn 4+ ion concentration is ∼0.8 mol% in SZM:Mn 4+ phosphor. Fluorescence lifetime of SZM:Mn 4+ phosphor decreases from ∼132 μs to 108 μs with increasing Mn 4+ ion concentration in the range of 0.2–1.0 mol%. Time-resolved spectra and fluorescence lifetime data indicate that luminescent center is caused by Mn 4+ ion. The luminous mechanism of SZM:Mn 4+ phosphor is explained by Tanabe-Sugano energy level diagram of Mn 4+ ion. The results are useful to understand the influences of the neighboring coordination environment around Mn 4+ and host crystal structure to the luminescence properties of Mn 4+ ion and develop other novel Mn 4+ -doped materials. [ABSTRACT FROM AUTHOR]

Sr 3 (VO 4 ) 2 :Eu 3+ and Sr 3 (VO 4 ) 2 :Eu 3+ , Li + phosphors are synthesized by solid-state reaction method in air. X-ray diffraction patterns indicate that all samples are pure phase Sr 3 (VO 4 ) 2 . The host Sr 3 (VO 4 ) 2 with excitation 348 nm emits yellow-green light. Emission spectrum of Sr 3 (VO 4 ) 2 :Eu 3+ phosphor with excitation 335 nm contains a broad emission band peaking at ∼540 nm due to V 5+ → O 2− charge transfer and some narrow emission bands owing to the 4 f – 4 f electron transations of Eu 3+ ion in the range of 400–780 nm. With excitation 394 nm, only emision bands derived from Eu 3+ ion are observed. Emission intensity of Sr 3 (VO 4 ) 2 :Eu 3+ phosphor can be improved obviously due to charge compensation and fluxing agent role of Li + ion when Li + ion is co-doped. The optimal Eu 3+ doping concentration is ∼5 mol%. The energy transfer process between [VO 4 ] 3− group and Eu 3+ ion is observed and analyzed by emission spectrum in Sr 3 (VO 4 ) 2 :Eu 3+ phosphor. The luminous mechanism of Sr 3 (VO 4 ) 2 :Eu 3+ phosphor is explained by energy transfer and energy level diagram of [VO 4 ] 3− group and Eu 3+ ion. [ABSTRACT FROM AUTHOR]

Novel NaAl 11 O 17 :Mn 2+ green phosphor is synthesized by solid-state reaction method in air. The emission band peaking at ~508 nm is observed owing to the 4 T 1 → 6 A 1 ( 6 S) transition of Mn 2+ ion, and the chromaticity coordinates are (0.0725, 0.6468). The excitation band peaking at ~360, 382, 424, 450, and 490 nm are attributed to 6 A 1 ( 6 S)→ 4 E( 4 D), 4 T 2 ( 4 D), [ 4 A 1 ( 4 G), 4 E( 4 G)], 4 T 2 ( 4 G), and 4 T 1 ( 4 G) transitions of Mn 2+ ion, respectively, which indicate that NaAl 11 O 17 :Mn 2+ phosphor may be excited by (near) ultraviolet and blue LED chip. The luminous mechanism is explained by Tanabe–Sugano diagram of Mn 2+ ion. The optimal Mn 2+ doping concentration is ~3.5 mol%. The NaAl 11 O 17 :3.5%Mn 2+ phosphor shows high quantum efficiency of ~67.84% with excitation 424 nm. The lifetime decreases from 6.72 to 6.0 ms with increasing Mn 2+ concentration in the range of 0–4 mol%. [ABSTRACT FROM AUTHOR]

Novel double perovskite Li 3 Mg 2 NbO 6 :Mn 4+ deep red-emitting phosphor is synthesized by solid-state reaction method in air. Emission band peaking at ∼670 nm with chromaticity coordinates (0.722, 0.278) is observed in the range of 600–780 nm due to 2 E → 4 A 2 transition of Mn 4+ ion. Excitation spectrum monitored at 670 nm contains three excitation bands peaking at ∼310, 395, and 470 nm within the range 220–600 nm, which indicate that Li 3 Mg 2 NbO 6 :Mn 4+ phosphor can be excited by ultraviolet, near ultraviolet, and blue light-emitting diode chips. The optimal Mn 4+ doping concentration is about 0.4 mol%. Fluorescence lifetime decreases from 0.485 to 0.32 ms with increasing Mn 4+ ion concentration from 0.2 to 1.2 mol%. Time resolved emission spectra and lifetime data confirm that there is only a single type of Mn 4+ ion luminescent center in Li 3 Mg 2 NbO 6 :Mn 4+ phosphor. The possible luminous mechanism of Mn 4+ ion is analyzed by Tanabe–Sugano energy diagram. [ABSTRACT FROM AUTHOR]

• Novel Ca 3 La 6 Si 6 O 24 :Eu3+ phosphors are synthesized successfully in air conditions. • Ca 3 La 6 Si 6 O 24 :Eu3+ phosphor with excited at 280 and 394 nm emits orange-red light. • Ca 3 La 6 Si 6 O 24 :Eu3+ phosphor shows an excellent thermal stability with the E a value ∼0.3314 eV. • The luminous and temperature quenching mechanisms are explained. Ca 3 La 6 Si 6 O 24 :Eu3+ phosphors are synthesized in air through high-temperature solid-state reaction method. The crystal structure, morphology, and luminescence properties are investigated. Ca 3 La 6 Si 6 O 24 :Eu3+ phosphor emits orange-red light in the range of 570–750 nm due to the 5D 0 → 7F S (S = 0, 1, 2, 3, and 4) transitions of Eu3+ ion. The optimal Eu3+ doping concentration is ∼8 mol%. The energy transfer mechanism is the electric multipolar interactions. The luminescence lifetimes are ∼1.70, 1.66, 1.62, 1.57, 1.51, and 1.49 ms for x = 2, 4, 6, 8, 10, and 12 mol%, respectively. Ca 3 La 6 Si 6 O 24 :Eu3+ phosphor shows excellent thermal stability with the E a value ∼0.3314 eV. The luminous and temperature quenching mechanisms are explained by the energy level diagram and configurational coordinate diagram of Eu3+ ions, respectively. The experimental results indicate that Ca 3 La 6 Si 6 O 24 :Eu3+ phosphor has a potential application in white light-emitting diodes (LEDs) based on the near UV (394 nm) LED chip. [ABSTRACT FROM AUTHOR]