Thermal diffusivity measurement of copper selenide using photoflash technique

For several past decades, the studies on the thermal properties of copper selenides (CuSe) have excluded thermal diffusivity even though thermal diffusivity directly reflects the combined effects of thermal conductivity, specific heat and density of materials put together. In this report the resear...

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Main Author:	Mat Daud, Norni Hidayawati
Format:	Thesis
Language:	English
Published:	2012
Subjects:	Thermal diffusivity Selenides Thermal diffusivity
Online Access:	http://psasir.upm.edu.my/id/eprint/31944/1/FS%202012%2043R.pdf
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spelling	my-upm-ir.319442015-01-19T07:47:47Z Thermal diffusivity measurement of copper selenide using photoflash technique 2012-02 Mat Daud, Norni Hidayawati For several past decades, the studies on the thermal properties of copper selenides (CuSe) have excluded thermal diffusivity even though thermal diffusivity directly reflects the combined effects of thermal conductivity, specific heat and density of materials put together. In this report the research findings of the thermal diffusivity of CuSe as measured by using photoflash technique at the temperature range from 80 K to room temperature are presented. The samples of CuSe which were based on the formula of CuxSe1-x were prepared using solid state method. The first set of the samples was prepared with similar x=0.5 composition, and each of the pellets was sintered at different sintering temperature from 150 to o 275 C for four days. The second and third sets of the samples were prepared by varying Cu composition with x = 0.3, 0.4, 0.5, 0.6, 0.7, and each set was sintered at 250 and o 275 C respectively for four days. XRD micrograph indicates that all the diffraction peaks were indexed to hexagonal CuSe phase for the samples with x = 0.5 and 0.6, and sintered at o 250 C upwards. However,the samples with x = 0.7 and were sintered at o 250 C and o 275 C had cubic Cu2Se single-phase while the sample with x = 0.8 and sintered at o 250 C had Cu2Se phase with two different crystallographic forms of monoclinic and cubic crystal structure. The sample with the most symmetrical crystal structure, which was cubic crystal structure was found to have highest thermal diffusivity while a distorted and the least symmetrical crystal structure was found to have lowest thermal diffusivity. SEM micrograph and density measurement showed that the grain size as well as density increased with the increase of sintering temperature, and with the increase of x up to 0.7. On the other hand the specific heat data showed a decreasing trend with increasing sintering temperature and increasing x. However the specific heat only slightly increased as the sample’s thermal diffusivity measuring temperature increased in the range of 80-300 K,showing that the specific heat was more or less independent of temperature. The grain size that increased with the sintering temperature affected the increased in the measured thermal diffusivity. In the bigger grain size samples, phonons would encounter lesser number of grain boundaries, experiencing a longer apparent mean free path and lower phonon-phonon scattering; the thermal diffusivity inevitably becomes higher. The similar increasing trend of thermal diffusivity was also observed for the samples with the increasing x. The thermal diffusivity was consistently decreased with increasing measuring temperature from 80 to 300 K, for all samples. At the very low temperature, the phonon-phonon relaxation time is very long due to the phonon occupation probability which is very low. When the temperature increases, a higher population of thermally excited phonons is expected causing the number of phonon collisions to increase. Thus lattice scattering lowers the thermal carrier mobility more and more at higher temperature due to the smaller mean free path. Therefore, their ability to transport heat away from the source is less, thus decreasing the thermal diffusivity value of this sample. The thermal diffusivity of the CuSe for all set of samples was in the range of (0.225-5.268) mm2/s at the temperature of 80 K to 300 K. Thermal diffusivity Selenides Photography, Flash-light 2012-02 Thesis http://psasir.upm.edu.my/id/eprint/31944/ http://psasir.upm.edu.my/id/eprint/31944/1/FS%202012%2043R.pdf application/pdf en public masters Universiti Putra Malaysia Thermal diffusivity Selenides Photography, Flash-light Faculty of Science
institution	Universiti Putra Malaysia
collection	PSAS Institutional Repository
language	English
topic	Thermal diffusivity Selenides Thermal diffusivity
spellingShingle	Thermal diffusivity Selenides Thermal diffusivity Mat Daud, Norni Hidayawati Thermal diffusivity measurement of copper selenide using photoflash technique
description	For several past decades, the studies on the thermal properties of copper selenides (CuSe) have excluded thermal diffusivity even though thermal diffusivity directly reflects the combined effects of thermal conductivity, specific heat and density of materials put together. In this report the research findings of the thermal diffusivity of CuSe as measured by using photoflash technique at the temperature range from 80 K to room temperature are presented. The samples of CuSe which were based on the formula of CuxSe1-x were prepared using solid state method. The first set of the samples was prepared with similar x=0.5 composition, and each of the pellets was sintered at different sintering temperature from 150 to o 275 C for four days. The second and third sets of the samples were prepared by varying Cu composition with x = 0.3, 0.4, 0.5, 0.6, 0.7, and each set was sintered at 250 and o 275 C respectively for four days. XRD micrograph indicates that all the diffraction peaks were indexed to hexagonal CuSe phase for the samples with x = 0.5 and 0.6, and sintered at o 250 C upwards. However,the samples with x = 0.7 and were sintered at o 250 C and o 275 C had cubic Cu2Se single-phase while the sample with x = 0.8 and sintered at o 250 C had Cu2Se phase with two different crystallographic forms of monoclinic and cubic crystal structure. The sample with the most symmetrical crystal structure, which was cubic crystal structure was found to have highest thermal diffusivity while a distorted and the least symmetrical crystal structure was found to have lowest thermal diffusivity. SEM micrograph and density measurement showed that the grain size as well as density increased with the increase of sintering temperature, and with the increase of x up to 0.7. On the other hand the specific heat data showed a decreasing trend with increasing sintering temperature and increasing x. However the specific heat only slightly increased as the sample’s thermal diffusivity measuring temperature increased in the range of 80-300 K,showing that the specific heat was more or less independent of temperature. The grain size that increased with the sintering temperature affected the increased in the measured thermal diffusivity. In the bigger grain size samples, phonons would encounter lesser number of grain boundaries, experiencing a longer apparent mean free path and lower phonon-phonon scattering; the thermal diffusivity inevitably becomes higher. The similar increasing trend of thermal diffusivity was also observed for the samples with the increasing x. The thermal diffusivity was consistently decreased with increasing measuring temperature from 80 to 300 K, for all samples. At the very low temperature, the phonon-phonon relaxation time is very long due to the phonon occupation probability which is very low. When the temperature increases, a higher population of thermally excited phonons is expected causing the number of phonon collisions to increase. Thus lattice scattering lowers the thermal carrier mobility more and more at higher temperature due to the smaller mean free path. Therefore, their ability to transport heat away from the source is less, thus decreasing the thermal diffusivity value of this sample. The thermal diffusivity of the CuSe for all set of samples was in the range of (0.225-5.268) mm2/s at the temperature of 80 K to 300 K.
format	Thesis
qualification_level	Master's degree
author	Mat Daud, Norni Hidayawati
author_facet	Mat Daud, Norni Hidayawati
author_sort	Mat Daud, Norni Hidayawati
title	Thermal diffusivity measurement of copper selenide using photoflash technique
title_short	Thermal diffusivity measurement of copper selenide using photoflash technique
title_full	Thermal diffusivity measurement of copper selenide using photoflash technique
title_fullStr	Thermal diffusivity measurement of copper selenide using photoflash technique
title_full_unstemmed	Thermal diffusivity measurement of copper selenide using photoflash technique
title_sort	thermal diffusivity measurement of copper selenide using photoflash technique
granting_institution	Universiti Putra Malaysia
granting_department	Faculty of Science
publishDate	2012
url	http://psasir.upm.edu.my/id/eprint/31944/1/FS%202012%2043R.pdf
_version_	1747811637570568192

Thermal diffusivity measurement of copper selenide using photoflash technique

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