Synthesis and thermoelectric power measurements of TlGaSe 2 single crystals
TlGaSe2single crystals were grown by modified Bridgman method. Thermoelectric power measurement were carried out in a brass working chamber designed for this purpose, allow measurements in a wide range of temperature under vacuum. The experimental results indicates that TlGaSe2 is of p-type conductivity. Throughout these measurements, various parameters such as effective mass of charge carriers, carrier mobility, diffusion coefficient, relaxation time and diffusion length for both majority and minority carriers were found. In addition to these pronounced parameters, the efficiency of the thermoelectric element (figure of merit) was evaluated, which leads to better application in many fields. [A. T. Nagat, S. A. Hussein, S. E. Al Garni. Synthesis and thermoelectric power measurements of TlGaSe2 single crystals. Life Sci J 2014;11(8):418-422]. (ISSN:1097-8135). http://www.lifesciencesite.com. 54
The optical investigation of TlGa0.999Pr0.001Se2 and TlGaSe2 single crystals
Abstract TlGaSe2 and TlGa0.999Pr0.001Se2 single crystals were grown by a method which is similar to the direct freezing method. They did not have cracks and voids on their surface. The freshly cleaved crystals had a mirror-like surface and there was no need for mechanical treatment. The absorption measurements were carried out on TlGaSe2 and TlGa0.999Pr0.001Se2 samples in the temperature range 10–320 K with a step of 10 K. The phonon energies calculated for TlGaSe2 and TlGa0.999Pr0.001Se2 are 34 and 26 meV, respectively. At 320 K, the direct band gaps of TlGaSe2 and TlGa0.999Pr0.001Se2 are 2.173 and 2.155 eV and the indirect band gaps are 2.054 and 2.044 eV, respectively. There are abrupt changes in the Urbach energy for TlGaSe2 at 180 and 210 K, and for TlGa0.999Pr0.001Se2 at 140 K. These temperatures obtained from the changing of Urbach energy may be phase transition temperatures.
Mathematical Time and Physical Time in the Theory Of Relativity
In the Theory of Relativity time is an imaginary quantity that can not be observed; it is a multiplication of a number that indicates duration of material change and number i that is an imaginary number. i on the square is -1. Time i⁄t is a mathematical time that describes the speed and the duration of material change. In the Universe one can observe physical time only as a stream of material change. It is not that change run in physical time, change itself is physical time.. Distinction between imaginary mathematical time and visible physical time opens some new perspectives into interpretation of Theory of Relativity. c