Samarium doped lead-zinc-phosphate glasses having composition(60-x)P_(2)O_(5)-20PbO-20ZnO-xSm_(2)O_(3) where x=0,0.5,1.0,3.0mol%were prepared by using the melt quenching technique.The Archimedes method was used to mea...Samarium doped lead-zinc-phosphate glasses having composition(60-x)P_(2)O_(5)-20PbO-20ZnO-xSm_(2)O_(3) where x=0,0.5,1.0,3.0mol%were prepared by using the melt quenching technique.The Archimedes method was used to measure their densities,which are used to calculate the molar volumes.The values of densities lie in the range 3.698–4.090 gm/cm^(3) whereas those of molar volume lie in the range of 37.24–40.00 cm^(-3).UV-vis-NIR absorption spectroscopy in the wavelength range 200–2000 nm was carried out.Absorption spectra consist of seven absorption peaks corresponding to the transitions from the 6H5/2 ground state to various excited energy levels.The energy band gap measured from the optical absorbance is found to be in the range of 3.88–4.43 eV and 3.68–4.33 eV for direct and indirect transitions,respectively.In addition,the photoluminescence spectrum shows four prominent emission bands centered at 560,597,642 and 700 nm corresponding to the 4G5/2–6HJ(J=5/2,7/2,9/2,11/2)transitions respectively and the intensity of all the bands are enhanced as the concentration of Sm3+ions increases.展开更多
Novel ceramics from waste material made of(x) paper ash–(80-x) cullet–20 kaolin clay(10 wt% ≤ x ≤ 30 wt%) were successfully synthesized using a conventional solid-state reaction technique. Energy-dispersive X-ray ...Novel ceramics from waste material made of(x) paper ash–(80-x) cullet–20 kaolin clay(10 wt% ≤ x ≤ 30 wt%) were successfully synthesized using a conventional solid-state reaction technique. Energy-dispersive X-ray analysis confirmed the presence of Si, Ca, Al, and Fe in the waste material for preparing these ceramics. The influence of the cullet content on the phase structures and the dielectric properties of these ceramics were systematically investigated. The impedance spectra were verified in the range from 1 Hz to 10 MHz at room temperature. The phase of the ceramics was found to primarily consist of wollastonite(CaSiO_3), along with minor phases of γ-dicalcium silicate(Ca_2SiO_4) and quartz(SiO_2). The sample with a cullet content of 55 wt% possessed the optimum wollastonite structure and exhibited good dielectric properties. An increase of the cullet content beyond 55 wt% resulted in a structural change from wollastonite to dicalcium silicate, a decrease in dielectric constant, and an increase in dielectric loss. All experimental results suggested that these novel ceramics from waste are applicable for electronic devices.展开更多
A series of（90–x）Li2B4O7-10Nb2O5-xNd2O3 glass samples（x=0, 5 mol.%, 10 mol.%, 15 mol.%, 20 mol.% and 25 mol.%） were synthesized using melt quenching technique. X-ray diffraction（XRD）, differential thermal analy...A series of（90–x）Li2B4O7-10Nb2O5-xNd2O3 glass samples（x=0, 5 mol.%, 10 mol.%, 15 mol.%, 20 mol.% and 25 mol.%） were synthesized using melt quenching technique. X-ray diffraction（XRD）, differential thermal analyzer（DTA）, Fourier transformed infrared（FTIR）, ultraviolet-visible-near-infrared（UV-Vis-NIR） spectrometer and photoluminescence（PL） spectroscopic characterizations were made to examine the influence of Nd3＋ concentration on the physical, structural and optical properties. Various physical properties such as glasses density, molar volume, thermal stability, ion concentration, polar on radius, inter-nuclear distance, field strength, cut-off wavelength, energy band gap and Urbach energy were calculated. The samples were amorphous in nature and confirmed from XRD pattern. The FTIR spectra revealed the presence of BO3 and BO4 functional groups. UV-Vis-NIR spectra exhibited nine prominent bands centered at 353, 430, 475, 524, 583, 681, 745, 803, 875 nm corresponding to the transitions from the ground state to ^4D（3/2）, ^2P（1/2）, ^2G（9/2）, ^4G（7/2）, ^4G（5/2）, ^4F（9/2）, ^4F（7/2）, ^4F（5/2）, ^4F（3/2） excited states, respectively. Moreover, the emission spectra at 355 nm excitation displayed three peaks centered at 903 nm（^4F（3/2）→^4I（9/2））, 1059 nm（^4F（3/2）→^4I（11/2）） and 1333 nm（^4F（3/2）→^4I（13/2））, respectively. Fluorescence lifetime was recorded between 53.69 to 28.43 μs. It was found that varying concentration of Nd^（3＋） ions strongly affected the physical, structural and optical properties of the glass samples.展开更多
The melt quenching method is used to prepare erbium-doped silver nanoparticle(NP)embedded phosphate glass.The effect of annealing on the glass on the formation of silver NPs produced by the reduction of silver(Ag^(+)...The melt quenching method is used to prepare erbium-doped silver nanoparticle(NP)embedded phosphate glass.The effect of annealing on the glass on the formation of silver NPs produced by the reduction of silver(Ag^(+)→Ag^(o))is studied.The glass samples are characterized by x-ray diffraction,UV-vis-NIR absorption,photoluminescence spectroscopy and transmission electron microscopy(TEM)imaging.The absorption spectra reveal not only the peaks due to Er^(3+)ions,but also the surface plasmon resonance band of silver NPs located around~442 nm.The TEM imaging shows the homogeneous distribution of silver NPs of almost spherical shape with an average diameter of~5 nm.Upconversion luminescence spectra show two major emissions at 550 and 638 nm,originating from the 4S_(3/2)and 4F_(9/2)energy levels of the Er^(3+)ions,respectively.The enhancement in the luminescence intensity of both the green and red bands is found to be due to the effective local field of the silver NPs as well as the energy transfer from the nanoclusters,comprised of centers with silver ions bound to silver atoms in dimers or trimers to Er^(3+)ions,whereas quenching occurred due to the energy transfer from erbium ions to silver NPs(Er^(^(3^(+)))→Ag^(o)).展开更多
The highly accurate full-potential linearized augmented plane wave plus local orbital method is employed to calculate the structural,electronic and transport properties of HgIn_(2)S_(4) and ZnIn_(2)S_(4).For ZnIn_(2)S...The highly accurate full-potential linearized augmented plane wave plus local orbital method is employed to calculate the structural,electronic and transport properties of HgIn_(2)S_(4) and ZnIn_(2)S_(4).For ZnIn_(2)S_(4),the calculated In–S bond length is in good agreement with the experimental data.Bulk moduli results suggest that ZnIn_(2)S_(4) can afford more compressional effects than HgIn_(2)S_(4).The present study confirms that both HgIn_(2)S_(4) and ZnIn_(2)S_(4) are indirect band gap materials with band gap values of 0.705 eV and 1.533 eV respectively.The localized region existing in the most bottom valance band of both materials splits into states by 1 eV energy difference under the spin orbital coupling effect.Contour plots of charge density predict that chemical bonding in these compounds is a mixture of ionic and covalent characteristics.Effective mass results reveal that mobility of charge carriers in ZnIn_(2)S_(4) is greater than that in HgIn_(2)S_(4).展开更多
Electronic and optical properties of small silicon quantum dots having 3 to 44 atoms per dot with and without surface passivation are investigated by computer simulation using the pseudo-potential approach.An empirica...Electronic and optical properties of small silicon quantum dots having 3 to 44 atoms per dot with and without surface passivation are investigated by computer simulation using the pseudo-potential approach.An empirical pseudo-potential Hamiltonian,a plane-wave basis expansion and a basic tetrahedral structure with undistorted local bonding configurations are used.The structures of the quantum dots are relaxed and optimized before and after hydrogen passivation.It is found that the gap increases more for a hydrogenated surface than the unpassivated one.Thus,both quantum confinement and surface passivation determine the optical and electronic properties of Si quantum dots.Visible luminescence is probably due to the radiative recombination of electrons and holes in the quantum-confined nanostructures.The effect of passivation of the surface dangling bonds by hydrogen atoms and the role of surface states on the gap energy is also examined.The results for the density of states,the dielectric function,the frequency dependent optical absorption cross section,the extinction coefficient and the static dielectric constants of the size are presented.The importance of the confinement and the role of surface passivation on the optical effects are discussed.展开更多
基金Supported by RMC through research grant of Q.J130000.7126.02J77/GUP and IDF UTM.J.10.01/13.14//128(201009M10001)Universiti Teknologi Malaysia.
文摘Samarium doped lead-zinc-phosphate glasses having composition(60-x)P_(2)O_(5)-20PbO-20ZnO-xSm_(2)O_(3) where x=0,0.5,1.0,3.0mol%were prepared by using the melt quenching technique.The Archimedes method was used to measure their densities,which are used to calculate the molar volumes.The values of densities lie in the range 3.698–4.090 gm/cm^(3) whereas those of molar volume lie in the range of 37.24–40.00 cm^(-3).UV-vis-NIR absorption spectroscopy in the wavelength range 200–2000 nm was carried out.Absorption spectra consist of seven absorption peaks corresponding to the transitions from the 6H5/2 ground state to various excited energy levels.The energy band gap measured from the optical absorbance is found to be in the range of 3.88–4.43 eV and 3.68–4.33 eV for direct and indirect transitions,respectively.In addition,the photoluminescence spectrum shows four prominent emission bands centered at 560,597,642 and 700 nm corresponding to the 4G5/2–6HJ(J=5/2,7/2,9/2,11/2)transitions respectively and the intensity of all the bands are enhanced as the concentration of Sm3+ions increases.
基金the financial support from the Ministry of Higher Education, Universiti Teknologi Malaysia via Grants of Vote: 08H42 and 4F752
文摘Novel ceramics from waste material made of(x) paper ash–(80-x) cullet–20 kaolin clay(10 wt% ≤ x ≤ 30 wt%) were successfully synthesized using a conventional solid-state reaction technique. Energy-dispersive X-ray analysis confirmed the presence of Si, Ca, Al, and Fe in the waste material for preparing these ceramics. The influence of the cullet content on the phase structures and the dielectric properties of these ceramics were systematically investigated. The impedance spectra were verified in the range from 1 Hz to 10 MHz at room temperature. The phase of the ceramics was found to primarily consist of wollastonite(CaSiO_3), along with minor phases of γ-dicalcium silicate(Ca_2SiO_4) and quartz(SiO_2). The sample with a cullet content of 55 wt% possessed the optimum wollastonite structure and exhibited good dielectric properties. An increase of the cullet content beyond 55 wt% resulted in a structural change from wollastonite to dicalcium silicate, a decrease in dielectric constant, and an increase in dielectric loss. All experimental results suggested that these novel ceramics from waste are applicable for electronic devices.
基金Project supported by the Ministry of Higher Education(Malaysia)(4F412)Postgraduate Fellowship Universiti Teknologi Malaysia(UTM)
文摘A series of（90–x）Li2B4O7-10Nb2O5-xNd2O3 glass samples（x=0, 5 mol.%, 10 mol.%, 15 mol.%, 20 mol.% and 25 mol.%） were synthesized using melt quenching technique. X-ray diffraction（XRD）, differential thermal analyzer（DTA）, Fourier transformed infrared（FTIR）, ultraviolet-visible-near-infrared（UV-Vis-NIR） spectrometer and photoluminescence（PL） spectroscopic characterizations were made to examine the influence of Nd3＋ concentration on the physical, structural and optical properties. Various physical properties such as glasses density, molar volume, thermal stability, ion concentration, polar on radius, inter-nuclear distance, field strength, cut-off wavelength, energy band gap and Urbach energy were calculated. The samples were amorphous in nature and confirmed from XRD pattern. The FTIR spectra revealed the presence of BO3 and BO4 functional groups. UV-Vis-NIR spectra exhibited nine prominent bands centered at 353, 430, 475, 524, 583, 681, 745, 803, 875 nm corresponding to the transitions from the ground state to ^4D（3/2）, ^2P（1/2）, ^2G（9/2）, ^4G（7/2）, ^4G（5/2）, ^4F（9/2）, ^4F（7/2）, ^4F（5/2）, ^4F（3/2） excited states, respectively. Moreover, the emission spectra at 355 nm excitation displayed three peaks centered at 903 nm（^4F（3/2）→^4I（9/2））, 1059 nm（^4F（3/2）→^4I（11/2）） and 1333 nm（^4F（3/2）→^4I（13/2））, respectively. Fluorescence lifetime was recorded between 53.69 to 28.43 μs. It was found that varying concentration of Nd^（3＋） ions strongly affected the physical, structural and optical properties of the glass samples.
基金Supported by RMC,UTM and MOHE through the research grant VOTE 06J33,06J39 and IDF UTM.J.10.01/13.14//128(201009M10001).
文摘The melt quenching method is used to prepare erbium-doped silver nanoparticle(NP)embedded phosphate glass.The effect of annealing on the glass on the formation of silver NPs produced by the reduction of silver(Ag^(+)→Ag^(o))is studied.The glass samples are characterized by x-ray diffraction,UV-vis-NIR absorption,photoluminescence spectroscopy and transmission electron microscopy(TEM)imaging.The absorption spectra reveal not only the peaks due to Er^(3+)ions,but also the surface plasmon resonance band of silver NPs located around~442 nm.The TEM imaging shows the homogeneous distribution of silver NPs of almost spherical shape with an average diameter of~5 nm.Upconversion luminescence spectra show two major emissions at 550 and 638 nm,originating from the 4S_(3/2)and 4F_(9/2)energy levels of the Er^(3+)ions,respectively.The enhancement in the luminescence intensity of both the green and red bands is found to be due to the effective local field of the silver NPs as well as the energy transfer from the nanoclusters,comprised of centers with silver ions bound to silver atoms in dimers or trimers to Er^(3+)ions,whereas quenching occurred due to the energy transfer from erbium ions to silver NPs(Er^(^(3^(+)))→Ag^(o)).
基金Supported by Fund of the Ministry of Higher Education(MOHE)Malaysia under Grant No Q.J130000.2526.02H93Universiti Teknologi Malaysia(UTM)under Grant No JI30000.2526.03H78.
文摘The highly accurate full-potential linearized augmented plane wave plus local orbital method is employed to calculate the structural,electronic and transport properties of HgIn_(2)S_(4) and ZnIn_(2)S_(4).For ZnIn_(2)S_(4),the calculated In–S bond length is in good agreement with the experimental data.Bulk moduli results suggest that ZnIn_(2)S_(4) can afford more compressional effects than HgIn_(2)S_(4).The present study confirms that both HgIn_(2)S_(4) and ZnIn_(2)S_(4) are indirect band gap materials with band gap values of 0.705 eV and 1.533 eV respectively.The localized region existing in the most bottom valance band of both materials splits into states by 1 eV energy difference under the spin orbital coupling effect.Contour plots of charge density predict that chemical bonding in these compounds is a mixture of ionic and covalent characteristics.Effective mass results reveal that mobility of charge carriers in ZnIn_(2)S_(4) is greater than that in HgIn_(2)S_(4).
基金by the RMC,UTM under Grant Nos 4D005/RMC and Q.J130000.7126.00J39/GUP.
文摘Electronic and optical properties of small silicon quantum dots having 3 to 44 atoms per dot with and without surface passivation are investigated by computer simulation using the pseudo-potential approach.An empirical pseudo-potential Hamiltonian,a plane-wave basis expansion and a basic tetrahedral structure with undistorted local bonding configurations are used.The structures of the quantum dots are relaxed and optimized before and after hydrogen passivation.It is found that the gap increases more for a hydrogenated surface than the unpassivated one.Thus,both quantum confinement and surface passivation determine the optical and electronic properties of Si quantum dots.Visible luminescence is probably due to the radiative recombination of electrons and holes in the quantum-confined nanostructures.The effect of passivation of the surface dangling bonds by hydrogen atoms and the role of surface states on the gap energy is also examined.The results for the density of states,the dielectric function,the frequency dependent optical absorption cross section,the extinction coefficient and the static dielectric constants of the size are presented.The importance of the confinement and the role of surface passivation on the optical effects are discussed.
