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The nearly pure green and red emissions of Ho 3+ /Yb 3+ co-doped Gd 2 (MoO 4 ) 3 were realized by tri-doping Eu 3+ and Ce 3+ , respectively. The Ho 3+ /Yb 3+ co-doped Gd 2 (MoO 4 ) 3 powder, radiating intense green and red emissions, was prepared by a typical sol-gel method. Under the excitation of 980 nm laser, the red-to-green ratio was tuned from 0.2 to 4 as the concentration of Eu 3+ changed from 6 to 0 mol%, attributed to the energy transfer processes between Ho 3+ and Eu 3+ . Meanwhile, the red-to-green ratio altered from 4 to 20 as the concentration of Ce 3+ changed from 0 to 20 mol% via the cross relaxing processes between Ho 3+ and Ce 3+ . The prepared phosphors, possessing large tuning range of red-to-green ratio and resisting high temperature, can be potentially applied to colorful display and solid-state lighting. [ABSTRACT FROM AUTHOR]

The methods of modulating emitting color are greatly important for up-conversion phosphors to broaden their applications, ranging from information storage to surface display. In this paper, the Ho 3+ /Tm 3+ /Yb 3+ tri-doped Gd 2 (MoO 4 ) 3 phosphors are synthesized by typical sol-gel method. It is found that the phosphors can radiate intense blue (475 nm), green (542 nm) and red (660 nm) up-conversion luminescence under 980 nm or 915 nm laser excitation. Especially, the emission color of the phosphors can be tuned from red to lavender by adjusting the excitation power of 980 nm or 915 nm continuous lasers. In addition, the up-conversion luminescence is also investigated under the excitation of 980 nm pulse laser. The emission color varies from green to blue and green to yellow by altering the pulse width and frequency, respectively. Combining the above methods, multi-color and white light are realized, indicating the potential application in dynamic colorful display. [ABSTRACT FROM AUTHOR]

A strategy to improve the sensitivity of NaLuF 4 :Yb 3+ /Er 3+ is elaborated via incorporation Mn 2+ ions, which results a closed energy transfer between Er 3+ and Mn 2+ ions ( 4 S 3/2 (Er 3+ ) → 4 T 1 (Mn 2+ ) → 4 F 9/2 (Er 3+ )). The NaLuF 4 :Yb 3+ /Er 3+ and NaLuF 4 :Yb 3+ /Er 3+ /Mn 2+ phosphors are prepared by a hydrothermal method. Notably, incorporation Mn 2+ for NaLuF 4 :Yb 3+ /Er 3+ phosphor rusults in enhancing the red to green intensity ratio, which acts as a bridge for energy transfer between 4 S 3/2 and 4 F 9/2 levels of Er 3+ . The temperature sensing behaviors of two phosphors are investigated in the 295–595 K range using a ratiometric technique under 980 nm excitation. Based on thermally ( 2 H 11/2 and 4 S 3/2 ) and non-thermally ( 4 F 9/2 and 4 S 3/2 ) coupled levels of Er 3+ , the influences of this energy transfer are discussed in detail. The sensitivity of NaLuF 4 :Yb 3+ /Er 3+ doping with Mn 2+ ions based on non-thermally coupled levels is much higher than that without Mn 2+ ions based on both thermally and non-thermally coupled levels in the 295–525 K range. The maximum sensitivity is 10.99 × 10 −3 K −1 at 295 K for NaLuF 4 :Yb 3+ /Er 3+ /Mn 3+ phosphor. These meaning results indicate that incorporation Mn 2+ ions in NaLuF 4 :Yb 3+ /Er 3+ phosphor is an effective method for enhancing sensitivity in the 295–525 K range. [ABSTRACT FROM AUTHOR]

Although lanthanide doped luminescent materials have been extensively investigated, a quantitative analysis of how temperature affects upconversion luminescence is still incomplete. The Gd 2 (MoO 4 ) 3 :Er 3+ /Yb 3+ phosphor is synthetized by sol-gel method. Based on the absorption spectra of Er 3+ ions, J-O intensity parameters and radiative transition probabilities are computed to estimate the optical properties. In view of ion-phonon interaction, the phonon-assisted energy transfer and multiphonon relaxation are responsible for the temperature dependent luminescence. Additionally, cross relaxation probability for 4 I 11/2 + 4 I 11/2 → 4 I 15/2 + 4 F 7/2 is determined to be 240 s −1 through quantitative simulation of ion-ion interaction. These meaningful results are of vital values for the field of laser crystal and optical temperature sensing. [ABSTRACT FROM AUTHOR]