Defect and Diffusion Forum Vol. 347

Abstract: Luminescence is "cold light", light from other sources of energy, which can take place at normal and lower temperatures. There are several varieties of luminescence, each named according to what the source of energy is, or what the trigger for the luminescence is. Luminescence is a collective term for different phenomena where a substance emits light without being strongly heated, i.e., the emission is not simply thermal radiation. This definition is also reflected by the term "cold light".

Abstract: The present review article contains various applications of Thermoluminescence. The phenomena of thermoluminescence (TL) or thermally stimulated luminescence (TSL) and optically stimulated luminescence (OSL) are widely used for measurement of radiation doses from ionizing radiations, viz. x-rays, γ rays and β particles. The applications of TL are initiated in the field of Geology followed by Archaeology, personal dosimetry, material characterization and many more to name. The TL technique has been found to be useful in dating specimens of geologically recent origin where all other conventional methods fail. It has been found to be highly successful in dating ancient pottery samples. The TL/OSL dating is done from a quartz grain, which is collected from pottery or brick, by reading the TL-output. The main basis in the Thermoluminescence Dosimetry (TLD) is that TL output is directly proportional to the radiation dose received by the phosphor and hence provides the means of estimating the dose from unknown irradiations. The TL dosimeters are being used in personnel, environmental and medical dosimetry. During the last two decades, OSL based dosimeters have also been used for various applications. Natural and induced TL signals can be used to explore mineral, oil and natural gas. The present review presents TL theory, TL of minerals, salt, cement, salt crystals from pickles, and low temperature thermoluminescence (LLTL) of few agricultural products. Contents of Paper

Abstract: Thermoluminescence (TL) is the thermally stimulated emission of light from an insulator or a semiconductor following the previous absorption of energy from ionizing radiation. TL dosimetry is used in many scientific and applied fields such as radiation protection, radiotherapy, industry, and environmental and space research, using many different materials. The basic demands of a thermoluminescent dosimeter (TLD) are good reproducibility, low hygroscopicity, and high sensitivity for very low dose measurements and good response at high doses in radiotherapy and in mixed radiation fields. In this review, we have discussed the past developments and the future opportunities in TLD materials and our efforts to make better future use of low cost materials in TLD applications. For this we have studied and discussed two efficient TLD phosphors with low cost and simple method of preparation on large scale for TLD materials. One of the phosphors is LiF:Mg,Cu,P (LiF: MCP), and another one is LiCaAlF₆:Eu, which has the potential to replace conventionally used CaSO₄:Dy TL dosimeter. LiF: MCP and LiCaAlF₆: Eu phosphors are potential candidates for TL dosimetry and could be good replacement for commercially available phosphors. Apart from this, we have also studied thermoluminescence in Aluminate and Borate materials. We have discussed in detail all three types of TLD materials. First, our study includes complete detail of material properties, methods and dosimetric characterizations of LiF: MCP Phosphor; second, it includes a new TL Dosimeter, LiCaAlF₆: Eu and its dosimetric characterizations; and lastly on some TL properties of Li₅AlO₄: Mn and MgB₄O₇: Dy,Na. In this review, we discus some recent developments in radiation dosimetry with regards to the measurement techniques and material preparations. Although many materials have been and are currently being studied for TLD, still there is a scope for the improvement in the material properties useful for the TLD, and the synthesis of new, more suitable materials. Contents of Paper

Abstract: Nowadays, luminescence dating technique has become one of the unique tools for paleoclimatic studies. A lot of progress has been made in terms of understanding the phenomenon of luminescence, development of methodology for luminescence dating and its application. Still there are several directions which require better understanding and refinement. This brief review article focuses on the different aspects of luminescence dating, covering basic theory behind luminescence and luminescence dating, procedural aspects, complications and issues of luminescence dating and future perspective.

Abstract: Elastico-mechanoluminescence (EML) is a type of luminescence induced by elastic deformation of solids. The present paper reports the elastic-ML of thermoluminescent crystals such as X-or γ-irradiated alkali halide crystals, ZnS:Mn, and ultraviolet irradiated persistent luminescent crystals. Generally, all the elastico-mechanoluminescent crystals are thermoluminescent, but all the thermoluminescent crystals are not the mechanoluminescent. The elastico-mechanoluminescence spectra of crystals are similar to their thermoluminescence spectra. Both the elastico-mechanoluminescence and thermoluminescence arise due to the de-trapping of charge carriers. As elastico-ML of persistent luminescent crystals depends on both the density of filled traps and piezoelectric field, the intense thermoluminescent crystals may not be the intense mechanoluminescent crystals. When a sample of X-or γ-irradiated alkali halide crystal, UV-irradiated persistent luminescent microcrystals mixed in epoxy resin, or a film of ZnS:Mn nanoparticles is deformed in the elastic region by the pressure rising at fixed pressing rate for a particular time, or by a pressure of triangular form, or by a pressure pulse, then after a threshold pressure, initially the EML intensity increases with time, attains a maximum value and later on it decreases with time. In the first case, the fast decay time of EML is related to the time-constant for stopping the moving crosshead of the testing machine; in the second case, generally the fast decay does not appear; and in the third case, the fast decay time is equal to the rise time of the pressure pulse. However, in all the cases, the slow decay time is related to the lifetime of re-trapped charge carriers in the shallow traps lying in the region where the piezoelectric field is negligible. When the sample is deformed by the pressure rising at fixed pressing rate for a particular time, or pressure of triangular form, then the ML appears after a threshold pressure and the transient EML intensity increases linearly with the applied pressure; however, the total EML intensity increases quadratically with the applied pressure. The EML intensity of persistent luminescent crystals decreases with increasing number of pressings. However, when these crystals are exposed to UV light, then the recovery of EML intensity takes place. The mechanical interaction between the bending segment of dislocations and filled electron traps is able to explain the elastico-ML of X-or γ-irradiated alkali halide crystals. However, the piezoelectrically-induced de-trapping model is suitable for explaining the ML of persistent luminescent crystals and ZnS:Mn. The investigation of elastico-ML may be helpful in understanding the thermoluminescence and the investigation of thermoluminescence may be helpful in understanding elastico-ML. Furthermore, similar to the thermoluminescence, the mechanoluminescence may also find application in radiation dosimetry. Expressions are derived for the elastico-ML of thermoluminescent crystals, in which a good agreement is found between the experimental and theoretical results. Finally, the application of the elasticoML of thermoluminescent crystals in light sources, displays, imaging devices, sensing devices, radiation dosimetry and in non-destructive testing of materials are discussed.Contents of Paper

Abstract: The use of thermoluminescence (TL) as a method for radiation dosimetry of ionizing radiation has been established for many decades and has found many useful applications in various fields, such as personnel and environmental monitoring, retrospective dosimetry, medical dosimetry, space dosimetry, high-dose dosimetry. Method of preparation, studies and applications of thermoluminescence (TL) dosimetric materials are reviewed. Several high sensitivity thermoluminescent dosimeters (TLDs) are now commercially available in different physical forms. These commercial TL dosimeters comply with a set of stringent requirements stipulated by the International Electrotechnical Commission (IEC). Specific features of TL phosphors for thermal neutron, fast neutron and high-energy charged particle (HCP) dosimetry are also considered. Some of the recent developments in the field of optically stimulated luminescence (OSL) and radiophotoluminescence (RPL) are also summarized. Comparative advantages of TL, OSL and RPL dosimeters are given. Results of recent studies of TL in nanosized materials are briefly presented. Future challenges in this field will also be discussed. Contents of Paper

Abstract: Growing apprehensions of radiological accidents and terroristic attacks have intensified research efforts to find materials with appropriate radiation sensitivity that are carried close to human body, are ubiquitously available and which can be used as fortuitous dosimeters in rapid determination of doses of individuals after radiation exposure. In this respect, thermoluminescence (TL) and optically stimulated luminescence (OSL) of chip cards and electronic components of personal objects have been recently evaluated by researchers in several countries. OSL and TL signal of chip cards is attributed to SiO₂ grains contained in the epoxy layers used for controlling the thixotropic properties whereas the radiation induced signal in electronic components (resistors, resonators, capacitors, ICs, antenna switches, etc.) of personal objects (mobile phones, USB flash drive, MP3 players, etc.) is attributed to the ceramic contents, especially to Al₂O₃ based substrates.

Abstract: The paper presents some results of study based on applications of ZnS core shell quantum dots (QDs) doped with Cu. Keeping the luminous properties in focus we synthesized the core shell QDs by chemical precipitation route, resulting in formation of core@shell QDs with ZnS core doped with copper and ZnS shell on it, i.e. [ZnS:Cu@Zn. We focus the application of these particles in field of OLEDs (AMOLED) to address the performance deficiencies like varying brightness of the different wavelength emitting LEDs, called Green Window problem. Efforts have been done to address the problems by synthesizing highly luminescent green emitting copper doped ZnS, core@shell QDs. Further a monolayer of core shell quantum dots was deposited on ITO by spin coating for analyzing the photometric properties of the QDs.