Spectroscopy and enhanced frequency upconversion in Nd3+-Yb3+ codoped TPO glasses: energy transfer and NIR to visible upconverter

Constructing high sensitivity thermometry with dual-emitting Nd3+/Er3+/Yb3+ codoped BaWO4 single crystal material

Inorganic oxides doped with rear earth(RE) have attracted much interest because of their outstanding optical properties. In this paper, the BaWO₄:Yb³⁺/Er³⁺/Nd³⁺ phosphors were successfully prepared by typical solid state method. The crystalline structure of the samples was characterized through X-ray diffraction(XRD). The morphology of that was demonstrated with field emission scanning electron microscopy(FE-SEM). Under 980 nm excitation, the BaWO₄: Yb³⁺/Er³⁺/Nd³⁺ phosphor presented four typical emissions at green(524-550 nm, Er³⁺), red(∼655 nm, Er³⁺), near infrared(∼710 nm, ∼820 nm, Nd³⁺). Furthermore, the temperature sensing properties of the samples were investigated in the temperature range of 303-573 K. The fluorescence intensity ratio(FIR) technique based on thermal and non-thermal coupled levels was applied to analyse the sensing performances. For BaWO₄:Yb³⁺/Er³⁺/Nd³⁺ phosphor, the maximum absolute sensitivity reached 0.0423 K^-1 at 303 K, which is based on ²H_11/2(Er³⁺) and ⁴F_7/2(Nd³⁺) levels. The repeatability of temperature response also was proved through four cold and heat cycles. The above result indicated that the BaWO₄:Yb³⁺/Er³⁺/Nd³⁺ phosphor would be a promising temperature sensing materials.

Recent progress in lanthanide-doped luminescent glasses for solid-state lighting applications-a review

Nowadays, solid-state white light-emitting diodes (wLEDs) have attracted remarkable attention for applications in general lighting, displays and numerous electronical devices due to their eminent efficiency, longer lifetime and higher mechanical durability compared to traditional incandescent and fluorescent lights. In current commercial wLEDs, a combination of Y₃Al₅O₁₂:Ce³⁺yellow phosphor with blue LED chip and epoxy resin is generally used to generate white light. However, there are some considerable frailties mostly originated from phosphor and resin such as, degradation upon heat, and moisture, inhomogeneous spectral distribution, and poor color rendering capability. Therefore, phosphor embedded glass-ceramics have been developed as a promising way to obtain durable solid-state lighting devices. However, in these methods, there is a greater risk of reactions between the phosphor material and the glass host. At this point, lanthanide-doped luminescent glasses have drawn great attention as a new generation phosphor and/or epoxy free white-light-emitting source owing to their favorable properties including high thermal and chemical stability, high transparency, and easy manufacturing process. This review article aims to comprehensively summarize the recent progress in singly (i.e., Dy³⁺, Eu²⁺), doubly (i.e., Dy³⁺/Eu³⁺, Dy³⁺/Tm³⁺, Dy³⁺/Ce³⁺, Ce³⁺/Sm³⁺, Ce³⁺/Tb³⁺) and triply (i.e., Ce³⁺/Tb³⁺/Mn²⁺, Eu³⁺/Tb³⁺/Tm³⁺, Ce³⁺/Tb³⁺/Eu³⁺, Tm³⁺/Tb³⁺/Sm³⁺, Ce³⁺/Dy³⁺/Eu³⁺, Ho³⁺/Tm³⁺/Yb³⁺, Er³⁺/Tm³⁺/Yb³⁺) lanthanide-doped glasses for solid-state lighting applications through down-shifting and up-conversion emissions. Theoretical background including energy transfer mechanisms, glass synthesis methods, radiative and colorimetric properties are given in details. Finally, various effective strategies are highlighted that minimize the critical challenges associated with lanthanides-such as providing energy transfer from quantum dots or nanoparticles to lanthanides, and doping lanthanides in low phonon energy glass-to improve the white light emission of luminescent glasses and broaden their application areas.

Effect of the Addition of Pb3O4 and TiO2 on the Optical Properties of Er3+/Yb3+:TeO2-WO3 Glasses

Heavy metal oxide tungstate-based tellurite glasses TeO2-WO3 (TW) containing Er3+/Yb3+ ions have been prepared by the melting and quenching method. The optical absorption and upconversion (UC) emission studies for the doped/codoped glasses have been performed. The effect of the addition of Pb3O4 and TiO2 to the Er3+/Yb3+:TW glass on its physical properties, optical absorption, and UC emission spectra under 980 nm/808 nm excitations has been studied. A significant enhancement in the UC emission intensity lying in the green and red region has been observed on introducing Pb3O4 and TiO2 into the Er3+/Yb3+:TW glass. The improvement in the UC emission intensity and full width at half maximum of the bands have been explained on the basis of energy transfer, local field correction factor, and Urbach energy. The non-color tunability in the color emitted from the prepared Er3+/Yb3+:TWPTi glass upon near-infrared (NIR) excitation at different pump power has been reported. Also, the color-correlated temperature and color purity have been measured under both NIR excitations.

Collective substitutions of selective rare earths (Yb3+, Dy3+, Tb3+, Gd3+, Eu3+, Nd3+) in ZrO2: an exciting prospect for biomedical applications

The study aims to understand the significance of collective rare earth (RE3+) substitutions in ZrO2 structures for biomedical applications. The RE3+ ions namely Yb3+, Dy3+, Tb3+, Gd3+, Eu3+, and Nd3+ were selected and their concentrations were adjusted to obtain three different combinations. The influence of RE3+ on the crystal structure of ZrO2 alongside the absorption, luminescence, mechanical, magnetic, computed tomography (CT), magnetic resonance imaging (MRI) properties was explored. The concomitant effect of the average ionic size and RE3+ concentration determines the crystallization behavior of ZrO2 at elevated temperatures. The collective RE3+ substitutions exhibit both up-conversion and down-conversion emissions with their respective excitation at 793 and 350 nm. Nevertheless, increment in the concentration of RE3+ is found to be detrimental to the mechanical stability of ZrO2. The collective characteristics of multiple RE3+ demonstrate the potential of the investigated system in multimodal imaging applications. The unique luminescence characteristics of Eu3+ and Tb3+ are promising for fluorescence imaging while the presence of Dy3+, Tb3+, Gd3+ and Nd3+ unveils a paramagnetic response required for MRI. In addition, Dy3+ and Yb3+ contribute to the high X-ray absorption coefficient values suitable for X-ray CT imaging.