A General Introduction to Luminescent Materials

Abstract

This chapter addresses those readers for who luminescent materials are a new challenge. Of course you are familiar with luminescent materials: you meet them everyday in your laboratory and in your home. If this should come as a surprise, switch on your fluorescent lighting, relax in front of your television set, or take a look at the screen of your computer. Perhaps you would like something more specialized. Remember then your visit to the hospital for X-ray photography. Or the laser in your institute; the heart of this instrument consists of a luminescent material. However, such a high degree of specialization is not necessary. The packet of washing powder in your supermarket also contains luminescent material. Now that we have been reminded of how full of luminescent materials our society is, the question arises "How do we define a luminescent material?" The answer is as follows: A luminescent material, also called a phosphor, is a solid which converts certain types of energy into electromagnetic radiation over and above thermal radiation. When you heat a solid to a temperature in excess of about 600"C, it emits (infra)red radiation. This is thermal radiation (and not luminescence). The electromagnetic radiation emitted by a luminescent material is usually in the visible range, but can also be in other spectral regions, such as the ultraviolet or infrared.Luminescence can be excited by many types of energy. Photoluminescence is excited by electromagnetic (often ultraviolet) radiation, cathodoluminescence by a beam of energetic electrons, electroluminescence by an electric voltage, triboluminescence by mechanical energy (e.g. grinding), X-ray luminescence by X rays, chemiluminescence by the energy of a chemical reaction, and so on. Note that thermoluminescence does not refer to thermal excitation, but to stimulation of luminescence which was excited in a different way. Fig. 1.1. A luminescent ion A in its host lattice. Exe: excitation; EM: emission (radiative return to the ground state); HEAT: nonradiative return to the ground state G. Blasse et al., Luminescent Materials

Identifying an efficient, thermally robust inorganic phosphor host via machine learning

“…Experimentally, S can be extracted by measuring the FWHM of the rare-earth substituted phosphor’s emission peak as a function of temperature and fitting these data with Eq. 7:where ℏω is the mean phonon energy and k B is the Boltzmann constant 59,60 . A system that has strong electron–phonon coupling (large Δ r ) tends to have S   >  5, whereas weak electron–phonon coupling (small Δ r ) occurs when S   <  1.…”

Aktuelle Entwicklungen auf dem Gebiet der anorganischen Leuchtstoffe

“…[51] Strahlungs-und Temperaturbeständigkeit werden durch Beschichtungen der Leuchtstoffpartikel mit AlPO 4 , Al 2 O 3 oder SiO 2 verbessert. [44] Die Emissionsleistung von BAM kann durch die Codotierung mit Nd 3+ oder Er 3+ signifikant erhöht werden, [52] [56][57][58] und somit die Qualität dieses Leuchtstoffs. Zur Unterdrückung der unerwünschten Emission nutzt man eine möglichst hohe TbKonzentration, bei der die Intensität der grünen Übergänge 5 D 3 !…”

Photoluminescent properties of Y1−xGdxVO4:Eu3+ powder phosphors

“…Also, GdVO 4 :Eu 3+ has been extensively studied in the field of lasers due to their stable physical and chemical properties [5,6]. In the fields of luminescent material, phosphors based on gadolinium compounds also play an important role because the Gd 3+ ion has its lowest excited levels at relatively high energy, which is due to the stability of the half-filled shell ground state [7,8]. GdVO 4 :Eu 3+ and YVO 4 :Eu 3+ are both excellent red emitting materials and these materials are applicable in many fields including cathode ray tubes, lamps, and X-ray detectors.…”