Understanding the quenching nature of Mn<sup>4+</sup>in wide band gap inorganic compounds: design principles for Mn<sup>4+</sup>phosphors with higher efficiency

et al. 2019

J. Mater. Chem. C

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

How to predict the location of the defect levels induced by 3d transition metal ions at octahedral sites of aluminate phosphors

Zhou

et al. 2019

J. Mater. Chem. C

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“…In contrast, the case of Nd 3+ shows a weak correlation in the temperature range from 240 K to 400 K. To better evaluate the lifetimes of the Mn 4+ and Nd 3+ ions, a two‐exponential equation was applied in the fitting process (Tables S2 and S3). The lifetime of the 2 E g excited state for Mn 4+ is reduced from 1.63 ms (78 K) to 2.72 μs (400 K), and the temperature‐dependent variation can be tackled with the following expression [Equation 1]: [53,55]

true τ_{a v - M n} = \frac{τ_{r} prefixtanh ((), h ν / 2 k_{B} T)}{1 + ((), \frac{τ_{r} tanh (h ν / 2 k_{B} T)}{τ_{n r}}) prefixexp ((), \frac{- Δ E_{M n - τ}}{k_{B} T})}

…”

Section: Resultsmentioning

confidence: 99%

Rational Design of a Nd³⁺‐Mn⁴⁺ Co‐doped Luminescent Thermometer: Towards High‐Sensitivity Temperature Sensing

Zhang

et al. 2021

ChemPhotoChem

High temperature sensitivity is an important development direction for luminescent thermometers, especially in the physiological temperature range. Herein, neodymium(III) and manganese(IV) ions were co‐doped into a yttrium gallium garnet host (YGG) and the relevant dopant concentrations were optimized in detail. The temperature‐dependent spectral survey indicates that when the temperature was above 240 K, the 2Eg→4A2g transition of Mn4+ and the 4F5/2→4I9/2 emission of Nd3+ show strong fluorescence quenching and gradual fluorescence enhancement, respectively. Such an apparent contrast mainly originates from the nonradiative cross‐relaxation between 2Eg (or 4T2g) and 4A2g states of Mn4+ and thermal coupling between the 4F5/2 and 4F3/2 levels of Nd3+, respectively. The obvious difference in fluorescence between the two luminescent ions leads to an excellent temperature sensing performance. The obtained relative sensitivity shows a maximum value at 280 K (7.90 % K−1) and maintains a magnitude above 5.00 % K−1 over the whole physiological temperature range. Moreover, the related temperature uncertainties are below 0.1 K from 298 K to 323 K, and the repeatability capability is larger than 98 %. The findings in this study offer a feasible approach to promote the sensing capability of temperature sensors by rationally designing co‐doping systems.

“…However, this type of WLED is not an ideal white light due to lack of essential red light component (lower color rendering index [CRI]), which can be technologically addressed by combining the yellow YAG:Ce 3+ phosphor with suitable red‐emitting phosphors . To this end, numerous red phosphor materials such as oxynitride, nitride, and aluminate phosphors, have been chosen to be compatible with the yellow phosphors and the underlying LED chips . So far, Eu 2+ or Ce 3+ ‐doped aluminates are shown as the most successful red‐emitting phosphors .…”

Section: Introductionmentioning

confidence: 99%

“…Mn 4+ , a typical transition metal ion with 3d 3 electron shell, is an ideal alternative to rare‐earth activators since it has a feature of two broad excitation bands in UV and blue region as well as series of sharp emission bands in deep red region, which practically meets the requirements for the red phosphors for WLEDs . As we have known, Mn ions often exhibit more than one valence state in phosphors.…”

Section: Introductionmentioning

confidence: 99%

The role of co‐dopants on the luminescent properties of α‐Al₂O₃:Mn⁴⁺ and BaMgAl₁₀O₁₇:Mn⁴⁺

et al. 2018

J Am Ceram Soc

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Mn 4+ doped aluminate materials with efficient red emission are promising components for warmer white light-emitting diodes. However, it still remains as a challenge on increasing its luminous efficiency. For Mn 4+ doped aluminate phosphors, co-dopants such as Li + , Mg 2+ , Na + , Si 4+ , or Ge 4+ ions are often added to tailor the photoluminescence properties of phosphors during preparing process. However, the role of the ions is still in debate. In this work we took BaMgAl 10 O 17 :Mn (BMA:Mn) and α-Al 2 O 3 :Mn as examples to study the effects of Li + , Mg 2+ , Na + , and Si 4+ on their luminescent properties. The energy levels induced by the co-dopants and some possible intrinsic defects of hosts (Al 2 O 3 )were calculated using the first-principles method. It is found that the Mg 2+ and Na + ions, compared with Li + and Si 4+ , can prefer to form hole-type defects which enhance the valence stability of Mn 4+ and thus enhance the emission intensity of the as-prepared phosphors.