Preparation of a phosphor, ZnA:Cu2+

Abstract

Phosphorescence is a fascinating phenomenon that we encounter every day. This paper is an outgrowth of an experiment that we have used in an undergraduate advanced inorganic chemistry course tor swrral ).;an. The purpose of this experiment is to famlllnrize the student with methods and equipment not encountered in other chemistry laboratory courses. This particular experiment exposes a student to the preparation of a doped semiconductor, phosphorescence, gettering procedures, reducing atmospheres, and the use of a high temperature furnace with associated thermocouples, temperature controllers, and temperature-sensing devices. There are several variables that can he changed during the course of several semesters or from student to student such as the temoerature. the nature and concentration of the dopant, and Eharacterization methods. The principles of excited states. hand theorv. and the structure of solids like ZnS are . .presented in the corresponding lecture part of this course.Other articles ( 1 . 2 ) have recentlv been ouhlished concerning phosphore&nt ZnS materials: It is the purpose of this paper to discuss the optical properties of inorganic materials, doped ZnS as a specific system and to point out the chemical considerations that need to he made in the preparation of a phosphor. The latter section of this paper dealswith our experimental procedure concerning the preparatiou of Cu2+-doped ZnS as a phosphor. The excitement that this experiment generates when a student observes phosphoresence under a black light after preparing this compound is truly amazing.Optical Properties of Inorganic Materials The production of light in certain minerals and insects a t normal temperature has fascinated scientists for over four centuries. The first recorded svnthetic luminescent material ~~~~~ ~~ was prepand in 1fiuR hy Casciarolo, n shoemaker from Holoma. lurl\.. who heiited a mixture o i the minrral l~arirp tBaSOJ andcha;coal. The resulting product glowed in the dark aftdr exnosure to sunlieht and was eiven the name ohosohor which . .is derived from thr Greek meaning "light bearer." I.att:r in Ififi!!. a German alchemist liennir Brand discovered a strange -. new element while heating "a secret, magical concoction" in a retort. This element which possessed an "eerie glow" was named phosphorus (this was the white polymorph of phosphorus, P4).In the middle of the 19th century,Stokes showed that the light emission from the mineral fluorite (CaF2) was a phenomenon involving the conversion of shorter wavelength, incident light into longer wavelength radiation (this is Stokes' law). He called the emitted light "fluorescence" and the incident source "exciting light." In addition, Stokes observed that the incident radiation always corresponded to an absorption hand in the material.Fluorescence is exhibited by many naturally occurring minerals such as scheelite (CaWOd, willemite (ZnnSi03, calcite (CaCOd, halo-apatites (Ca5(P04)3X), fluorite (CaF2), and wurtzite (ZnS). Synthetic samples of all these minerals have been shown t...

Determination of a Kinetic Law of Phosphorescence Decay Using a Conventional Photo Camera and Free Image Processing Software

“…2,19 This phosphor consists of ZnS crystals with admixtures of copper and gives a long-lasting green afterglow with λ max ∼ 520−530 nm. 20,21 The glow-inthe-dark object with the phosphorescence intensity shown in Figures 2−4 exhibits the afterglow of this particular characteristic color. The luminescence of the ZnS:Cu phosphor can be excited with blue light 21 and occurs via the recombination mechanism, with the emission centers being Cu + ions.…”

“…It should be noted that, in most inexpensive glow-in-the-dark children’s toys, ZnS:Cu phosphor is employed as the luminescent additive. , This phosphor consists of ZnS crystals with admixtures of copper and gives a long-lasting green afterglow with λ max ∼ 520–530 nm. , The glow-in-the-dark object with the phosphorescence intensity shown in Figures – exhibits the afterglow of this particular characteristic color. The luminescence of the ZnS:Cu phosphor can be excited with blue light and occurs via the recombination mechanism, with the emission centers being Cu + ions. ,,,, Although the compressed hyperbola law is the most common among crystal phosphors, and the ZnS:Cu phosphor is of greater abundance, when performing this work one can easily find objects that obey the exponential law and contain a luminescent additive another than ZnS:Cu.…”

Inorganic Phosphors for Teaching a Holistic Approach to Functional Materials Investigation: From Synthesis and Characterization to Applications of Thermo- and Mechanoluminescence

“…Empirically, this was found to result in a linear relationship between mechanluminescence intensity and impact force per unit area (pressure). 9 Previously reported undergraduate educational activities involving phosphor materials have focused mostly on copperdoped zinc sulfide, 6,10,11 with the goal of visually demonstrating luminescence mechanism or teaching the kinetic models using afterglow. The laboratory experiments on SrAl 2 O 4 :Eu,Dy phosphors reported in J. Chem.…”

“…Photons produced by the electrons relaxing from a trap within the band gap into the valence band are red-shifted relative to the initial excitation wavelength of light. Traditionally, afterglow phosphors have been primarily based on zinc sulfide. , Although widely used, zinc sulfide phosphors have some significant drawbacks such as being sensitive to moisture, as well as only maintaining its glow for relatively short periods of time (tens of minutes) in the dark. A class of materials that promises major improvements over zinc-sulfide-based phosphors are metal aluminates doped with lanthanide ions.…”

Microwave Synthesis of a Long-Lasting Phosphor

“…In recent years, there has been a increasing need for efficient long-lasting luminescent materials. During the past decades, the only commercial phosphorescent material was Cu (or Co)-doped zinc sulfide (ZnS) (1), but these materials could only glow for tens of minutes and were sensitive to moisture. The only alternative materials were phosphors containing radioactive ions such as promethium (Pm 3+ ), where the β-radiation coming from the disintegration of Pm ions is converted into visible light.…”