关于举行印度Maharaja Sayajirao University of Baroda 大学K.V. R Murthy教授学术报告会的通知
报告题目：Thermoluminescence and Applications & Synthesis of nano Phosphors
报 告 人：K.V. R Murthy（Maharaja Sayajirao University of Baroda）
报告时间：2016年12月4日（星期天）20:45 ~ 22:15
报告地点：发光材料与器件国家重点实验室402
报告人简介：
Dr. K.V. R Murthy is a professor of Maharaja Sayajirao University of Baroda. He got his Ph.D degree in M.S University in 1990. Then he became an associate professor in 1994. In 2002, he became a professor in Applied Physics Department, Faculty of Technology and Engineering, M.S University of Baroda. So far, he has editted 40 Volumes/Books on Luminescence and Applications, published more than 550 papers in various journals and conference proceedings and organized 10 international events in India and 75 national events as a collaborator / chairmen etc.. He is also a managing editor of International Journal of Luminescence and Applications. And he is a president of Luminescence Society of India from 2012 to 2018. Now he mainly focus on Light Emitting Diodes and Phosphors; Photoluminescence of lamp and display phosphors and applications; nano phosphors for display applications and Thermoluminescence and applications.
报告人摘要：
An increasing amount of public interest in environmental monitoring programmes is being focused on the environmental impact of radiation arising from nuclear power operations and the corresponding detection of slight variations in the natural radiation background. The primary objective of individual monitoring for external radiation is to assess, and thus limit, radiation doses to individual workers. Supplementary objectives are to provide information about the trends of these doses and about the conditions in places of work and to give information in the event of accidental exposure. The phenomenon of Thermoluminescence [TL] has been extensively studied by many investigators. The understanding of the mechanism of occurrence of thermally stimulated emission is the important in order to exploit its practical applications in various fields. Many researchers have suggested their views for TL mechanism for pure and impurity activated materials. With expanding knowledge of solid state physics, it is a topic of research to give latest possible mechanism of TL. However, the present understanding of TL has explored very high application potential of it in various fields. The modernization and development in the instrumentation; and better understanding of TL have helped the professional to solve their problems in many fields. The applications of the TL are summarized as: Archaeology , Biology, Biochemistry, Forensic Science, Geology, Medical Science (Nuclear medicine), Radiation Dosimetry (envorimental and accidental), Radiation Physics, SolidState Physics, Space Science, Spectroscopic Analysis, TL-Photography , Exploration of Radioactive Material (Like Uranium) from Earth, Exploration of Petroleum Product from earth crust etc.,
Thermoluminescent Dosimetry (TLD) has been developed during 1960-70 for various applications in medicine and industry. TLD, the most advanced and most intensively studied integrating dosimeter system, has now reached the stage at which it may replace or supplement film dosimetry. TLD systems are widely applied to environmental monitoring programmes near nuclear installations. TLD systems with high reproducibility in the milli roentgen dose range are required in order to measure exposures equal to that resulting from an exposure rate of 10µR h-1 during field periods of from several days up to a year. A brief list of applications specific to radiation oncology is given here. In radiation oncology dosimetric accuracy demanded is of the order of 2-5%. TLDs offer a clear solution since their precision meets this criteria.
A material can emit light either through incandescence, where all atoms radiate, or by luminescence, where only a small fraction of atoms, called emission centers or luminescence centers, emit light. In inorganic phosphors, these in homogeneities in the crystal structure are created usually by addition of a trace amount of dopants, impurities called activators. (In rare cases dislocations or other crystal defects can play the role of the impurity). The wavelength emitted by the emission center is dependent on the atom itself, and on the surrounding crystal structure.
The scintillation process in inorganic materials is due to the electronic band structure found in the crystals. An incoming particle can excite an electron from the valence band to either the conduction band or the exciton band (located just below the conduction band and separated from the valence band by an energy gap). This leaves an associated hole behind, in the valence band. Impurities create electronic levels in the forbidden gap. The excitons are loosely bound electron-hole pairs that wander through the crystal lattice until they are captured as a whole by impurity centers. The latter then rapidly de-excite by emitting scintillation light (fast component). In case of inorganic scintillators, the activator impurities are typically chosen so that the emitted light is in the visible range or near-UV where photomultipliers are effective. The holes associated with electrons in the conduction band are independent from the latter. Those holes and electrons are captured successively by impurity centers exciting certain metastable states not accessible to the excitons.
Phosphors used in high-resolution flat panel displays have more stringent requirements than traditional CRT phosphors. Specialized synthesis techniques were developed to precisely control particle size (<5 µm), particle size distribution, and particle shape of display phosphors. Hydrothermal synthesis, combustion synthesis, and spray processing are a few of these techniques that will be described. The development of colloidochemical synthesis techniques to produce nanocrystals has introduced.
Stress will be given on the Phosphor PbWO4 nanostructures synthesized via Low Temperature Hydrothermal (LTH) method at different pH without using any surfactant.
