The Experts below are selected from a list of 105 Experts worldwide ranked by ideXlab platform
K N R Taylor - One of the best experts on this subject based on the ideXlab platform.
-
spectral dependence of the acoustic properties of Proustite close to the 210 k phase transition
Journal of Physics: Condensed Matter, 1992Co-Authors: Xiaoli Zhao, J I Dunlop, K N R TaylorAbstract:Experimental results are presented for the ultrasonic velocity and attenuation of shear waves at 2.4 MHz in Proustite. The effects of the polarization and wavelength of irradiation in the range 450-900 nm on the photoinduced phase transition at 210 K are reported.
-
phase transitions in single crystals of Proustite ag3ass3
Phase Transitions, 1991Co-Authors: S R Yang, K N R TaylorAbstract:Abstract The previous work on the topic of phase transitions in Proustite is briefly reviewed. Study on the fundamental absorption edge related optical properties of Proustite is reported, which reveals anomalies in the average absorption coefficient, band gap energy and polarization shift at temperatures near 210 K. These anomalies together with the abnormal photodielectric behaviour observed in this study provide conclusive evidence for the existence of the photoinduced broad phase change near 210 K. The nature of this photoinduced phase change is assumed to be a displacive type ferroelectric phase transition with a relative displacement of the two sublattices resulting from the redistribution of silver ions under the action of illumination and cooling near to the phase transition temperature.
-
changes in the ultrasonic attenuation of Proustite at the photoinduced phase transition near 210 k
Journal of Physics: Condensed Matter, 1991Co-Authors: J I Dunlop, K N R Taylor, Xiaoli ZhaoAbstract:The ultrasonic attenuation in Proustite has been measured in the vicinity of 210 K. the results provide further evidence for a photoinduced phase transition at this temperature. A possible mechanism for the increase in attenuation induced by illumination is discussed.
-
ionic conductivity in single crystal Proustite ag3ass3
Journal of Applied Physics, 1991Co-Authors: S R Yang, K N R TaylorAbstract:The temperature dependent ac conductivity of single‐crystal Proustite measured at several frequencies over the temperature range from 82 to 467 K reveals six distinct regions associated with different conduction mechanisms. A phase transition from ionic to superionic conduction has been found to occur at a temperature of approximately 420 K. The frequency dispersion spectra obtained at different temperatures from 82 to 373 K, over the frequency range 10−2 to 103 Hz show two regions of frequency dependent conductivity. The dc conductivity and ionic hopping rate as well as the carrier densities have been extracted from the ac conductivity data. The results show that the ac conductivity of Proustite is characterized by low hopping rates and high carrier densities suggesting that the Ag+ ions may execute a long range hopping motion in the lattice. The relationship between the dc and ac components of conductivity have been critically examined and the results show that the ratio σdc/σac is thermally stimulated ...
-
Ionic conductivity in single‐crystal Proustite Ag3AsS3
Journal of Applied Physics, 1991Co-Authors: S R Yang, K N R TaylorAbstract:The temperature dependent ac conductivity of single‐crystal Proustite measured at several frequencies over the temperature range from 82 to 467 K reveals six distinct regions associated with different conduction mechanisms. A phase transition from ionic to superionic conduction has been found to occur at a temperature of approximately 420 K. The frequency dispersion spectra obtained at different temperatures from 82 to 373 K, over the frequency range 10−2 to 103 Hz show two regions of frequency dependent conductivity. The dc conductivity and ionic hopping rate as well as the carrier densities have been extracted from the ac conductivity data. The results show that the ac conductivity of Proustite is characterized by low hopping rates and high carrier densities suggesting that the Ag+ ions may execute a long range hopping motion in the lattice. The relationship between the dc and ac components of conductivity have been critically examined and the results show that the ratio σdc/σac is thermally stimulated ...
S R Yang - One of the best experts on this subject based on the ideXlab platform.
-
phase transitions in single crystals of Proustite ag3ass3
Phase Transitions, 1991Co-Authors: S R Yang, K N R TaylorAbstract:Abstract The previous work on the topic of phase transitions in Proustite is briefly reviewed. Study on the fundamental absorption edge related optical properties of Proustite is reported, which reveals anomalies in the average absorption coefficient, band gap energy and polarization shift at temperatures near 210 K. These anomalies together with the abnormal photodielectric behaviour observed in this study provide conclusive evidence for the existence of the photoinduced broad phase change near 210 K. The nature of this photoinduced phase change is assumed to be a displacive type ferroelectric phase transition with a relative displacement of the two sublattices resulting from the redistribution of silver ions under the action of illumination and cooling near to the phase transition temperature.
-
ionic conductivity in single crystal Proustite ag3ass3
Journal of Applied Physics, 1991Co-Authors: S R Yang, K N R TaylorAbstract:The temperature dependent ac conductivity of single‐crystal Proustite measured at several frequencies over the temperature range from 82 to 467 K reveals six distinct regions associated with different conduction mechanisms. A phase transition from ionic to superionic conduction has been found to occur at a temperature of approximately 420 K. The frequency dispersion spectra obtained at different temperatures from 82 to 373 K, over the frequency range 10−2 to 103 Hz show two regions of frequency dependent conductivity. The dc conductivity and ionic hopping rate as well as the carrier densities have been extracted from the ac conductivity data. The results show that the ac conductivity of Proustite is characterized by low hopping rates and high carrier densities suggesting that the Ag+ ions may execute a long range hopping motion in the lattice. The relationship between the dc and ac components of conductivity have been critically examined and the results show that the ratio σdc/σac is thermally stimulated ...
-
Ionic conductivity in single‐crystal Proustite Ag3AsS3
Journal of Applied Physics, 1991Co-Authors: S R Yang, K N R TaylorAbstract:The temperature dependent ac conductivity of single‐crystal Proustite measured at several frequencies over the temperature range from 82 to 467 K reveals six distinct regions associated with different conduction mechanisms. A phase transition from ionic to superionic conduction has been found to occur at a temperature of approximately 420 K. The frequency dispersion spectra obtained at different temperatures from 82 to 373 K, over the frequency range 10−2 to 103 Hz show two regions of frequency dependent conductivity. The dc conductivity and ionic hopping rate as well as the carrier densities have been extracted from the ac conductivity data. The results show that the ac conductivity of Proustite is characterized by low hopping rates and high carrier densities suggesting that the Ag+ ions may execute a long range hopping motion in the lattice. The relationship between the dc and ac components of conductivity have been critically examined and the results show that the ratio σdc/σac is thermally stimulated ...
-
temperature dependence of the frequency dependent negative photoconductivity and photodielectric effects in Proustite
Journal of Applied Physics, 1990Co-Authors: S R Yang, K N R TaylorAbstract:An exhaustive study of the photodielectric response of Proustite at various temperatures over the frequency range 10−2–103 Hz has revealed an extremely complex series of changes. These involve both negative and positive photoeffects which appear to arise from competing processes in the sample. A model based on a two‐layer dielectric system, in which one of the layers is established by space‐charge buildup at the electrode, appears to explain most of the observed results.
-
Temperature dependence of the frequency‐dependent negative photoconductivity and photodielectric effects in Proustite
Journal of Applied Physics, 1990Co-Authors: S R Yang, K N R TaylorAbstract:An exhaustive study of the photodielectric response of Proustite at various temperatures over the frequency range 10−2–103 Hz has revealed an extremely complex series of changes. These involve both negative and positive photoeffects which appear to arise from competing processes in the sample. A model based on a two‐layer dielectric system, in which one of the layers is established by space‐charge buildup at the electrode, appears to explain most of the observed results.
Simon A T Redfern - One of the best experts on this subject based on the ideXlab platform.
-
high temperature phase transitions dielectric relaxation and ionic mobility of Proustite ag3ass3 and pyrargyrite ag3sbs3
Journal of Applied Physics, 2002Co-Authors: Kristin A Schonau, Simon A T RedfernAbstract:The nature of phase transitions in natural and synthetic Proustite, Ag3AsS3, has been studied in darkness above 300 K and compared with its natural counterpart pyrargyrite, Ag3SbS3. The behavior of Proustite is characterized by silver ion mobility within the structure. Proustite and (to a lesser extent) pyrargyrite were investigated as a function of temperature by x-ray and neutron powder diffraction, dielectric spectroscopy, and dynamic mechanical analysis. At 305 K (280 K for pyrargyrite) Proustite undergoes a second-order phase transition, exhibiting a positive nonsymmetry breaking spontaneous strain of the unit cell, with thermal expansion along [001] changing from negative to positive. This strain results from the onset of thermally induced hopping of silver ions, as revealed by impedance spectroscopy. It may be described as an almost undamped Debye oscillator, which is not present below Tc (305 K) with an activation energy of 0.42 eV (0.40 eV for pyrargarite). Around 420 K the high-frequency conduct...
Sherif Kharbish - One of the best experts on this subject based on the ideXlab platform.
-
spectral structural characteristics of the extremely scarce silver arsenic sulfosalts Proustite smithite trechmannite and xanthoconite μ raman spectroscopy evidence
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2017Co-Authors: Sherif KharbishAbstract:Abstract The spectral - structural features of the rare silver arsenic (Ag-As) sulfosalts, Proustite, Ag3AsS3, and the extremely scarce smithite, AgAsS2, trechmannite, AgAsS2 and xanthoconite, Ag3AsS3, were studied by the μ-Raman technique. Stretching - bending vibrations of the pyramidal isolated and interconnected AsS3 groups were responsible for the Raman spectra of the studied sulfosalts. The symmetric and asymmetric stretching modes appear between 380 and 350 cm− 1, whereas those of bending (S As S) vibrations between 335 and 280 cm− 1. The As S longer bond lengths absolutely demonstrate the red shift (i.e. decrease in energy) from xanthoconite to trechmannite, smithite and Proustite and the lowering in FWHM in comparable vibrational modes.
Paul G Spry - One of the best experts on this subject based on the ideXlab platform.
-
crystallographic and chemical constraints on the nature of the Proustite pyrargyrite solid solution series
American Mineralogist, 2010Co-Authors: Luca Bindi, Giovanni Pratesi, Paul G SpryAbstract:The present paper reports a crystal-chemical study of minerals belonging to the Proustite–pyrargyrite group by evaluating 32 natural samples of Proustite and 27 samples of pyrargyrite from different localities that have variable chemical compositions. The unit-cell parameters were modeled as a function of the Sb contents. The a parameter is strongly influenced by the As ↔ Sb substitution, whereas the influence on the c parameter is very minor (nearly constant trend). The following equations were obtained from the linear fitting of the data: \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \begin{eqnarray*}&&\mathit{a}\_{pred}\ =\ 10.8433(3)\ +\ 0.2019(4)Sb\ (apfu)\\&&\mathit{c}\_{pred}\ =\ 8.7189(6)\ +\ 0.0059(9)Sb\ (apfu)\\&&\mathit{V}_{pred}\ =\ 887.77(7)\ +\ 34.0(1)Sb\ (apfu).\end{eqnarray*} \end{document} The crystal structure of the members of the Proustite–pyrargyrite solid solution consists of two sets of spiral chains parallel to the c -axis. Each chain contains alternating Ag and S atoms, with each chain being connected by As and Sb atoms, which are the apices of flat pyramidal AsS3/SbS3 groups. Each S atom is part of a different Ag-S chain. The compositional data support the concept that Proustite–pyrargyrite solid solutions re-equilibrate and exsolve to near end-member upon cooling. Examples of intermediate compositions are rare in nature and must have quenched above the solvus.
-
Crystallographic and chemical constraints on the nature of the Proustite–pyrargyrite solid-solution series
American Mineralogist, 2010Co-Authors: Luca Bindi, Giovanni Pratesi, Paul G SpryAbstract:The present paper reports a crystal-chemical study of minerals belonging to the Proustite–pyrargyrite group by evaluating 32 natural samples of Proustite and 27 samples of pyrargyrite from different localities that have variable chemical compositions. The unit-cell parameters were modeled as a function of the Sb contents. The a parameter is strongly influenced by the As ↔ Sb substitution, whereas the influence on the c parameter is very minor (nearly constant trend). The following equations were obtained from the linear fitting of the data: \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \begin{eqnarray*}&&\mathit{a}\_{pred}\ =\ 10.8433(3)\ +\ 0.2019(4)Sb\ (apfu)\\&&\mathit{c}\_{pred}\ =\ 8.7189(6)\ +\ 0.0059(9)Sb\ (apfu)\\&&\mathit{V}_{pred}\ =\ 887.77(7)\ +\ 34.0(1)Sb\ (apfu).\end{eqnarray*} \end{document} The crystal structure of the members of the Proustite–pyrargyrite solid solution consists of two sets of spiral chains parallel to the c -axis. Each chain contains alternating Ag and S atoms, with each chain being connected by As and Sb atoms, which are the apices of flat pyramidal AsS3/SbS3 groups. Each S atom is part of a different Ag-S chain. The compositional data support the concept that Proustite–pyrargyrite solid solutions re-equilibrate and exsolve to near end-member upon cooling. Examples of intermediate compositions are rare in nature and must have quenched above the solvus.
