Luminescence thermometry with transition metal ions. A review

Transition metal (TM) ion activated phosphors are increasingly being used as probes for luminescence thermometry. Their luminescence is characterized by strong absorption and emission bands that span the visible and near-infrared spectral ranges and are highly susceptible to temperature variations. Due to the latter characteristic, sensitive and reliable remote temperature measurements can be performed by observing temperature-induced changes in TM ion emission intensities, emission bandwidths and bandshifts, and excited state lifetimes, as well as the temperature dependences of the intensity ratios between various emission bands in single or double activated phosphors. This review provides a systematic analysis of the performances of luminescent thermometers based on different TM ions and discusses the relations among the TM spectroscopic properties, characteristics of the host material structure, and thermometric performance. Particular attention is given to the engineering of energy transfer between TM and other dopant ions to obtain highly sensitive thermometers. Finally, several typical application examples from recent literature are highlighted. © 2022 The Author(s

Submicron to Nanocrystalline α-Al2O3:Mn as a Promising Red-Emitting Luminescence Phosphor Candidate

This thesis aims to provide a detailed understanding of the storage properties of the α-Al2O3:Mn powder, encompassing various techniques, including photoluminescence (PL), thermoluminescence (TL), persistent luminescence (PersL), and spectral hole-burning. The α-Al2O3:Mn³⁺ sample was prepared via an exothermic combustion reaction method at 600 °C. The structural properties and elemental composition of the powder were investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray fluorescence (XRF). We explored the generation of Mn4+ in α-Al2O3:Mn³⁺ by soft X-ray (8 keV) exposure, focusing on its potential application in multilevel optical data storage. The small diffraction limit of the X-rays enables the implementation of an exceptionally fine pitch during the writing step. The results showed that ~100 levels can be read out, corresponding to 6-7 bits per data point encoding. The stored information (Mn⁴⁺) can be read out via the R-lines (²E → ⁴A₂) under ∼470 nm (⁴A₂ → ⁴T₂), or ∼630 nm (⁴A₂ → ²T₁) excitation. The data could be erased via exposure to blue light. We demonstrated the persistent luminescence properties of α-Al2O3:Mn⁴⁺, Mg²⁺ powder samples. We discussed factors that influence the efficiency of persistent luminescence, including dopant concentrations, temperatures, and trap levels. We also delved into the underlying principles of the persistent luminescence mechanism and studied the trap levels by analyzing the samples’ thermoluminescence glow curve. The photochemical persistent hole-burning properties in the R1 line transition were investigated in α-Al2O3:Mn³⁺ and α-Al2O3:Mn⁴⁺, Mg²⁺ powder samples. The hole-burning properties of Mn4+ ions burned via the R1 and R2 lines were measured either via the photoluminescence excitation mode by monitoring the luminescence of a vibrational sideband at ~694 nm, or in luminescence, with blue light excitation after burning. The hole widths were studied as a function of burn fluence and temperature, ranging from 2 to 90 K. We conducted an investigation into the luminescence properties of Mn4+ ions by introducing Gd3+ as co-dopants. We also performed Zeeman studies on a macroscopic crystal of Al2O3:Mn4⁺, Mg2+. Overall, this study provides an overview of the storage properties of α-Al2O3:Mn phosphors, providing valuable insights into their fundamental characteristics and practical applications

Advances in Functional Inorganic Materials Prepared by Wet Chemical Methods

Functional inorganic materials are an indispensable part of innovative technologies that are essential to the development of many fields of industry. The use of new materials, nanostructures, or multicomponent composites with specific chemical or physical properties promotes technological progress in electronics, optoelectronics, catalysis, biomedicine, and many other areas that are concerned with many aspects of human life. Due to the broad and diverse range of potential applications of functional inorganic materials, the development of superior synthesis pathways, reliable characterization, and a deep understanding of the structure–property relationships in materials are rightfully considered to be fundamentally important scientific issues. Only synergetic efforts of scientists dealing with the synthesis, functionalization and characterization of materials will lead to the development of future technologies

Tunable photoluminescence from rare earth and transition metal ions activated silicate glasses and glass ceramics

The motivation of this thesis is given in the introduction, followed by the corresponding background. The second chapter gives the results and discussions in the form of publications. Firstly, dual-mode PL of mixed valence Eu3+/Eu2+ doped glass ceramics are investigated. During the crystallization processes, Eu3+ ions are partially incorporated into crystalline phases, and gradually reduced to Eu2+. It is investigated how to control the blue PL of Eu2+ and red PL of Eu3+ in these glass ceramics. Secondly, tunable IVMn2+/VIMn2+ PL of Li2ZnSiO4 glass ceramics are displayed. The Mn2+ ions are octahedrally coordinated in the SLZAKP glass. After crystallization, Mn2+ can be partially incorporated into the crystalline phase. Consequently, the ratio of IVMn2+/VIMn2+ and the emission color can be tailored by annealing temperature. Thirdly, broadband PL of V5+ doped SLZAKP glasses and corresponding Li2ZnSiO4 glass ceramics are studied. The PL from [VO4]3– is centered at 550–590 nm. After crystallization, a tenfold increase in the emission intensity is observed. Fourthly, broadband NIR PL of VINi2+ doped Ba-Al titanate glass ceramics is investigated. Ni2+ ions are tetrahedrally coordinated in precursor glasses, whereas Ni2+-species are incorporated into the crystalline environment in octahedral sites. The broadband NIR PL of VINi2+ spans the spectral range of 1.0–1.6 μm. Decay kinetics of the emission band can be adjusted. Lastly in this chapter, DC of one blue photon to two NIR photons is obtained from the Pr3+/Yb3+ co-doped SLABS glasses and Mn2+/Yb3+ do-doped Zn2GeO4. Pr3+ ions act as sensitizers by absorbing 415–505 nm photons and transferring the absorbed energy to Yb3+ ions in a cooperative down-conversion process. In the Zn2GeO4 lattice, intrinsic defect transitions and Mn2+ ions act as broadband spectral sensitizers by absorbing UV-Vis photons. The absorbed energy is transferred to Yb3+ ions in a cooperative DC process. The third chapter summarizes the thesis