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Introduction to Borate Phosphors
Published in S. K. Omanwar, R. P. Sonekar, N. S. Bajaj, Borate Phosphors, 2022
Pritee K. Tawalare, A. B. Gawande
Phosphors are solid, luminescent materials that emit photons when excited by an external energy source, such as an electron beam (cathodoluminescence) or ultraviolet light (photoluminescence). Phosphors are composed of an inert host lattice, which is transparent to the excitation radiation and an activator, typically a 3d or 4f electron metal, which is excited under energy bombardment. The process of luminescence occurs by adsorption of energy at the activator site, relaxation, and subsequent emission of a photon and a return to the ground state. The efficiency of a phosphor depends on the amount of relaxation that occurs during the activation and emission. Relaxation is the process in which energy is lost to the lattice as heat; it needs to be minimized in order to extract the highest luminous efficiency. The luminous efficiency is defined as the ratio of the energy emitted to the energy absorbed.
Photon Detectors
Published in Antoni Rogalski, Zbigniew Bielecki, Detection of Optical Signals, 2022
Antoni Rogalski, Zbigniew Bielecki
Phosphors absorb X-ray photons and emit visible photons as a result of the returning to their ground state of the excited electrons in the material. Phosphors are generally used in a thin film layer of polycrystalline material and, hence, provide excellent spatial resolution, but they absorb X-rays relatively weakly. Usually, phosphors were combined with photographic films, but today they can be combined with a visible detector array to improve an X-ray detective system.
Synthesis and Luminescence Characteristics of Europium Doped Gadolinium Based Oxide Phosphors for Display and Lighting Applications
Published in Vikas Dubey, Sudipta Som, Vijay Kumar, Luminescent Materials in Display and Biomedical Applications, 2020
Jyoti Singh, Dirk Poelman, Vikas Dubey, Vinay Gautam
Phosphors are materials which are capable of emitting radiation when subjected to ultraviolet light, electron bombardment, X-rays or some other form of excitation (Antony et al. 2001). This emission is known as luminescence. Phosphors are mainly categorized into two types: organic and inorganic. A wide range of organic molecules and polymers are found to show luminescence. These so-called fluorophores find applications as luminescent labels for bio-imaging, as dyes, optical brighteners and in organic light emitting diodes (Sasabe and Kido 2013). This chapter is focused on the study of novel inorganic phosphors which are ideal for applications requiring long lifetimes, such as LEDs for lighting and displays. The inorganic phosphor is comprised of two components: (i) host lattice and (ii) the impurity or activator ions (mainly rare-earth ions or transition metals) (Kikuchi 2010; Smet et al. 2010, 2011; Avci et al. 2009; Poelman et al. 1993). Generally, inorganic phosphors are semiconductors or insulators with a wide band gap. Semiconductors with a wide and direct band gap are of great interest in the optical industry and have a wide range of applications in the field of optoelectronics, lasers, solid-state lighting, sensors, solar cell etc. (Bridot et al. 2007; Zhou et al. 2011; Vries et al. 2005).
Hydrometallurgical Roadmaps and Future Strategies for Recovery of Rare Earth Elements
Published in Mineral Processing and Extractive Metallurgy Review, 2023
C. Erust, M. K. Karacahan, T. Uysal
Phosphors are used as light emitting substances in different kind of lamps like fluorescent lamps (FLs), compact fluorescent lamps (CFLs), cathode ray tubes (CRTs), energy saving lamps (ESLs), and light-emitting diodes (LEDs). Recovery of REE from the phosphors is important due to instability in RE’s supply and the increasing of waste materials. Spent phosphors which are won by disintegration of lamps are landfilled till today in underground deposits due to the lack of industrial processes and their mercury content whereas the glass fraction is recycled and it is aimed to recover the rare earth elements it contains in last decade (Poscher et al. 2013). In researchers, it has been determined that spent phosphors contain up to 15–25% of rare earth elements (Y, Eu, Ce, Tb, Nd, Er, Gd, and Pr) (Ippolito et al. 2017). Many publications of recycling processes are available from spent phosphors to produce a mixture rare earth oxide and the extraction of single element-like yttrium and europium by hydrometallurgical methods (De Carolis et al. 2015; Innocenzi et al. 2017; Ippolito et al. 2017; Wang et al. 2011).
Dissimilarity measure of local structure in inorganic crystals using Wasserstein distance to search for novel phosphors
Published in Science and Technology of Advanced Materials, 2021
Shota Takemura, Takashi Takeda, Takayuki Nakanishi, Yukinori Koyama, Hidekazu Ikeno, Naoto Hirosaki
Phosphors are used for general lighting and display backlight. Transition metal ions and rare earth ions are used as an emitting ion for phosphors. The emitting color of the phosphors depends on the luminescence properties such as the peak wavelength and the emission spectral width. To realize a novel phosphor, the luminescence properties must be controlled. The emissions of Ce3+ and Eu2+ based on a 4 f-5d transition can be controlled by changing the local structure around the ions. An 8 K TV requires next-generation green and red Eu2+ phosphors with a narrow-band emission to satisfy BT.2020 standard. Eu2+ phosphors with a narrow-band emission are reported for CaF2 [1], BaSi2O2N2 [2], CaAl2S4 [3], β-Sialon [4–6], etc. The full width at half maximum (FWHM) of the emission spectrum also depends on the local structure in the phosphor. However, the ideal local structure with the narrowest FWHM is unknown theoretically. Since Eu2+ in CaF2, which is a simple crystal with a cubic local structure, and UCr4C4-type phosphors with a cubic-like local structure such as SrLiAl3N4:Eu2+ [7], SrMg3SiN4:Eu2+ [8], CaLiAl3N4:Eu2+ [9] and RbLi(Li3SiO4)2:Eu2+ [10] show a narrow-band emission, a crystal structure with a cubic local structure has been garnering attention as a novel narrow-band phosphor candidate.
Thermoluminescence properties and evaluation of trapping parameters of Eu3+ and Dy3+ activated K3Ca2(SO4)3Cl phosphors
Published in Radiation Effects and Defects in Solids, 2021
Nahida Baig, N.S. Dhoble, Yatish R. Parauha, Meenal Joshi, S.J. Dhoble
According to Mckeever et. al (1)., thermoluminescence is one of the processes of Thermally Stimulated Phenomena. By definition, thermoluminescence (TL) is the emission of light while heating of a solid sample, if irradiated earlier. The TL material absorbs energy during its exposure to radiation and stores this energy until it is heated (2). This phenomenon is depicted by glasses, ceramics, plastics and some organic solids. Over the last three decades, inorganic phosphors have been widely used in luminescent devices. TL spectroscopy has emerged as a crucial technique to understand the dynamics of electron trapping centers (3). The TL technique, normally utilized for dosimetry, also includes other important applications, such as dating of ancient archeological pottery samples, geological samples, TLD badge for whole body monitoring, in biology and biochemistry, quality control and several clinical applications (4). TL dosimetry is a low-cost, easy technique for measuring the radiation doses using TLD material (5,6). It is a well-established sensitive technique for recording changes in the defect concentration (7). Thermoluminescence from a material is very sensitive to the amount and nature of impurity, its thermal history and the defect pattern present in the material, etc.