The Experts below are selected from a list of 255 Experts worldwide ranked by ideXlab platform
D.yu. Kosyanov - One of the best experts on this subject based on the ideXlab platform.
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Al2O3–Ce:YAG and Al2O3–Ce:(Y,Gd)AG composite ceramics for high brightness lighting: Effect of microstructure
Materials Characterization, 2021Co-Authors: D.yu. Kosyanov, A P Zavjalov, Alexander M. Zakharenko, A.a. Vornovskikh, Xin Liu, A.a. Kosianova, O.o. Shichalin, V. Yu. Mayorov, Valery G. Kuryavyi, Xinglu QianAbstract:Abstract The paper studies efficient Al2O3–Ce:YAG and Al2O3–Ce:(Y,Gd)AG composite ceramic phosphors produced by reactive vacuum sintering. As one of the possible routes for microstructure optimization, effect of isothermal holding time was considered. The correlation between microstructural parameters (the ratio of average grain size of the matrix and thermally stable phase, Residual Porosity, grain and pore size distributions) and photoluminescent properties of sintered composite ceramics after combining them with a blue light-emitting diode was identified. The differences in thermal quenching behavior between Ce-doped and Ce,Gd-codoped systems were also discussed. The highest luminous efficiency of almost 151 lm/W (4526 K) and 133 lm/W (3808 K) was obtained for Al2O3–Ce:YAG, Al2O3–Ce:(Y,Gd)AG phosphors with garnet/alumina size ratio of 2.1 and 1.6, Residual Porosity of P = 0.0065 and 0.0047 vol%, respectively.
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A new method for calculating the Residual Porosity of transparent materials
Journal of Alloys and Compounds, 2019Co-Authors: D.yu. Kosyanov, R.p. Yavetskiy, S.v. Parkhomenko, A.g. Doroshenko, I.o. Vorona, A P Zavjalov, Alexander M. Zakharenko, A.a. VornovskikhAbstract:Abstract To quantify Residual Porosity of the materials is important when analyzing their microstructure and functional performance. The problem becomes particularly urgent for functional (optical, laser) materials. A common way to solve it is to calculate the quantity and size of pores on the sample's cross-section. However, authors do not pay special attention to experimental data processing. Present work studies pore size distribution in 1–4 at% Nd3+:YAG transparent ceramics using experimental measurements of pore sizes determined from the cross-section. Suggested method enables one to evaluate Residual Porosity correctly.
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The effect of Residual Porosity on the optical properties of Y 3 Al 5 O 12 :Nd 3+ laser ceramics
Technical Physics Letters, 2015Co-Authors: I.o. Vorona, D.yu. Kosyanov, R.p. Yavetskiy, S.v. Parkhomenko, A.g. Doroshenko, O. L. Shpilinskaya, A.v. Lopin, A. V. TolmachevAbstract:The relationship between the Residual Porosity, linear optical loss coefficient, and sintering temperature-time regime has been studied for Y3Al5O12:Nd3+ (4 at %) laser ceramics. It is experimentally established that the linear optical loss coefficient linearly depends on the magnitude of Residual Porosity. The slope efficiency of laser generation reached a value of 31% in ceramics with a Residual Porosity on a level of 0.0016 vol % that was obtained by reactive sintering at 1750°C for 12 h. The obtained results are important for optimization of the technology of Y3Al5O12:Nd3+ laser ceramics.
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Microstructure evolution of SiO2, ZrO2-doped Y3Al5O12:Nd3+ ceramics obtained by reactive sintering
Ceramics International, 2015Co-Authors: R.p. Yavetskiy, D.yu. Kosyanov, S.v. Parkhomenko, A.g. Doroshenko, I.o. Vorona, A.v. Lopin, A. V. Tolmachev, Pavel V. Mateychenko, V.n. Baumer, V.l. VoznyyAbstract:The evolution of microstructure, Porosity and optical properties of SiO2, ZrO2-doped Y3Al5O12:Nd3+ laser ceramics obtained by reactive sintering have been studied. The relationship between the relative density and average grain size of garnet ceramics obtained in the 1500–1800 °С temperature range has been determined. It has been shown that anomalous behavior of sintering trajectory at Т>1700 °С may be due to the inhibition of ceramic grain boundaries mobility by Zr4+ ions. At the sintering temperature of 1800 °С a partial decomposition of Y3Al5O12:Nd3+, Si4+, Zr4+ solid solution occurs with precipitation of alumina along grain boundaries of ceramics. The relationships between the Residual Porosity, in-line optical transmittance and sintering conditions of Y3Al5O12:Nd3+ (4 at%) ceramics have been studied. Optical ceramics sintered at T=1750 °C for 12 h possess Residual Porosity of 0.0016 vol%, in-line optical transmittance of 82.9% at 1064 nm wavelength and laser slope efficiency of 33% under diode-pumping at 808 nm.
Nachum Frage - One of the best experts on this subject based on the ideXlab platform.
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Improved alumina transparency achieved by high-pressure spark plasma sintering of commercial powder
Ceramics International, 2020Co-Authors: Barak Ratzker, Avital Wagner, Sergey Kalabukhov, Nachum FrageAbstract:Abstract Depending on starting powder and sintering conditions, alumina with extremely small grains and low Residual Porosity can be highly transparent. Combined with its excellent mechanical, thermal and chemical properties, transparent alumina is a promising material for a wide range of optical applications. In the present study, highly transparent alumina was fabricated by single-step high-pressure spark plasma sintering (HP-SPS) using raw commercial pure powder. The microstructure of the sintered alumina consists of fine grains with average size of ~170 nm and extremely fine Residual Porosity. The measured real in-line transmittance (RIT) was 72.6% at a wavelength of 640 nm, close to the calculated theoretical value (74.9%). The difference between theoretical and measured RIT was attributed to scattering by fine Residual pores. This conclusion was supported by Porosity analysis, and RIT calculations suggest that the Porosity volume fraction is about 0.005%. The combination of fine grain size and high level of transparency could be suitable for potential advanced alumina-based laser materials.
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Residual Porosity and optical properties of spark plasma sintered transparent polycrystalline cerium-doped YAG
Journal of the European Ceramic Society, 2019Co-Authors: Avital Wagner, Barak Ratzker, Sergey Kalabukhov, Maxim Sokol, Nachum FrageAbstract:Abstract Transparent cerium-doped yttrium aluminum garnet (Ce:YAG) phosphors are promising candidates for high-power white light emitting diode applications. In the present study, Ce:YAG powder was synthesized by a co-precipitation method and highly transparent ceramics were fabricated by spark plasma sintering. The effects of temperature and pressure, as well as post-sintering treatments (annealing or hot isostatic pressing), on Residual Porosity were studied by electron and confocal laser microscopy. Correlation between Residual Porosity characteristics (pore size and volume fraction) and optical properties (in-line transmittance and photoluminescence intensity) of the luminescent transparent ceramics was established.
A.a. Vornovskikh - One of the best experts on this subject based on the ideXlab platform.
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Al2O3–Ce:YAG and Al2O3–Ce:(Y,Gd)AG composite ceramics for high brightness lighting: Effect of microstructure
Materials Characterization, 2021Co-Authors: D.yu. Kosyanov, A P Zavjalov, Alexander M. Zakharenko, A.a. Vornovskikh, Xin Liu, A.a. Kosianova, O.o. Shichalin, V. Yu. Mayorov, Valery G. Kuryavyi, Xinglu QianAbstract:Abstract The paper studies efficient Al2O3–Ce:YAG and Al2O3–Ce:(Y,Gd)AG composite ceramic phosphors produced by reactive vacuum sintering. As one of the possible routes for microstructure optimization, effect of isothermal holding time was considered. The correlation between microstructural parameters (the ratio of average grain size of the matrix and thermally stable phase, Residual Porosity, grain and pore size distributions) and photoluminescent properties of sintered composite ceramics after combining them with a blue light-emitting diode was identified. The differences in thermal quenching behavior between Ce-doped and Ce,Gd-codoped systems were also discussed. The highest luminous efficiency of almost 151 lm/W (4526 K) and 133 lm/W (3808 K) was obtained for Al2O3–Ce:YAG, Al2O3–Ce:(Y,Gd)AG phosphors with garnet/alumina size ratio of 2.1 and 1.6, Residual Porosity of P = 0.0065 and 0.0047 vol%, respectively.
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A new method for calculating the Residual Porosity of transparent materials
Journal of Alloys and Compounds, 2019Co-Authors: D.yu. Kosyanov, R.p. Yavetskiy, S.v. Parkhomenko, A.g. Doroshenko, I.o. Vorona, A P Zavjalov, Alexander M. Zakharenko, A.a. VornovskikhAbstract:Abstract To quantify Residual Porosity of the materials is important when analyzing their microstructure and functional performance. The problem becomes particularly urgent for functional (optical, laser) materials. A common way to solve it is to calculate the quantity and size of pores on the sample's cross-section. However, authors do not pay special attention to experimental data processing. Present work studies pore size distribution in 1–4 at% Nd3+:YAG transparent ceramics using experimental measurements of pore sizes determined from the cross-section. Suggested method enables one to evaluate Residual Porosity correctly.
Craig Cook - One of the best experts on this subject based on the ideXlab platform.
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A 210Pb–226Ra–230Th–238U study of Klyuchevskoy and Bezymianny volcanoes, Kamchatka
Geochimica et Cosmochimica Acta, 2007Co-Authors: Simon Turner, Kenneth W.w. Sims, Mark K. Reagan, Craig CookAbstract:Abstract Lavas from Klyuchevskoy and Bezymianny volcanoes, Kamchatka, appear to show a link between the extent of partial melting in their mantle source region and the subsequent degree of fractionation suffered by the magmas during passage through the crust. This fractionation may have occurred on timescales significantly less than 1000 years if observed 226 Ra excesses largely reflect variable Residual Porosity in the source melting region. Unlike most arc lavas, those with the highest MgO contents and Ba/Th ratios have the lowest 226 Ra excess. Forward models suggest that those portions of the source which had undergone the greatest addition of U by fluids from the subducting plate also underwent the greatest extents of partial melting at the highest Residual Porosity. At Kluchevskoy, a change from eruption of high-MgO to high-Al 2 O 3 basaltic andesites around 1945 is reflected in an increase in size of 226 Ra excess which seems to require a simultaneous decrease in Residual Porosity and suggests a rapid changes in the melting regime. The eruption of andesites at Bezyminanny, simultaneous with the eruption of basaltic andesites at Klyuchevskoy, further suggests that different degree melts produced at differing Residual Porosity can be formed and extracted from the melt region at the same time. Thus, the melting processes beneath Klyuchevskoy and Bezyminanny are demonstrably complex. They have clearly been influenced by both fluid addition from the subducting plate and extension and decompression beneath the Central Kamchatka Depression. Finally, the 210 Pb data are, with one or two exceptions, in equilibrium with 226 Ra, suggesting that there was restricted relative magma-gas movement in this highly productive magmatic system.
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A ²¹⁰Pb-²²⁶Ra-²³⁰Th-²³⁸U study of Klyuchevskoy and Bezymianny volcanoes, Kamchatka
2007Co-Authors: Simon Turner, Kenneth W.w. Sims, Mark K. Reagan, Craig CookAbstract:Lavas from Klyuchevskoy and Bezymianny volcanoes, Kamchatka, appear to show a link between the extent of partial melting in their mantle source region and the subsequent degree of fractionation suffered by the magmas during passage through the crust. This fractionation may have occurred on timescales significantly less than 1000 years if observed Ra excesses largely reflect variable Residual Porosity in the source melting region. Unlike most arc lavas, those with the highest MgO contents and Ba/Th ratios have the lowest Ra excess. Forward models suggest that those portions of the source which had undergone the greatest addition of U by fluids from the subducting plate also underwent the greatest extents of partial melting at the highest Residual Porosity. At Kluchevskoy, a change from eruption of high-MgO to high-Al2O3 basaltic andesites around 1945 is reflected in an increase in size of Ra excess which seems to require a simultaneous decrease in Residual Porosity and suggests a rapid changes in the melting regime. The eruption of andesites at Bezyminanny, simultaneous with the eruption of basaltic andesites at Klyuchevskoy, further suggests that different degree melts produced at differing Residual Porosity can be formed and extracted from the melt region at the same time. Thus, the melting processes beneath Klyuchevskoy and Bezyminanny are demonstrably complex. They have clearly been influenced by both fluid addition from the subducting plate and extension and decompression beneath the Central Kamchatka Depression. Finally, the Pb data are, with one or two exceptions, in equilibrium with Ra, suggesting that there was restricted relative magma-gas movement in this highly productive magmatic system. ! 2007 Elsevier Ltd. All rights reserved.
R.p. Yavetskiy - One of the best experts on this subject based on the ideXlab platform.
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A new method for calculating the Residual Porosity of transparent materials
Journal of Alloys and Compounds, 2019Co-Authors: D.yu. Kosyanov, R.p. Yavetskiy, S.v. Parkhomenko, A.g. Doroshenko, I.o. Vorona, A P Zavjalov, Alexander M. Zakharenko, A.a. VornovskikhAbstract:Abstract To quantify Residual Porosity of the materials is important when analyzing their microstructure and functional performance. The problem becomes particularly urgent for functional (optical, laser) materials. A common way to solve it is to calculate the quantity and size of pores on the sample's cross-section. However, authors do not pay special attention to experimental data processing. Present work studies pore size distribution in 1–4 at% Nd3+:YAG transparent ceramics using experimental measurements of pore sizes determined from the cross-section. Suggested method enables one to evaluate Residual Porosity correctly.
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Effect of microstructural features on the laser efficiency of Nd3+:Y3Al5O12 ceramics
Quantum Electronics, 2015Co-Authors: I.o. Vorona, R.p. Yavetskiy, O. L. Shpilinskaya, A. V. Tolmachev, Yubai Pan, V.l. VoznyyAbstract:The optical properties and microstructure of transparent Nd3+:Y3Al5O12 ceramics synthesised by different reactive sintering routes are studied. It is found that the Residual Porosity of optical ceramics is directly related to the homogeneity of the microstructure of initial compacts, which can be estimated by the existence of particle agglomerates larger than 1 mm in initial nanopowders. A qualitative correlation is established between the Residual Porosity, the optical losses and the lasing slope efficiency of Nd3+:Y3Al5O12 ceramics. The maximum laser efficiency (η = 49%) was observed in the samples with the lowest Porosity (2.3 × 10-3 vol %).
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The effect of Residual Porosity on the optical properties of Y 3 Al 5 O 12 :Nd 3+ laser ceramics
Technical Physics Letters, 2015Co-Authors: I.o. Vorona, D.yu. Kosyanov, R.p. Yavetskiy, S.v. Parkhomenko, A.g. Doroshenko, O. L. Shpilinskaya, A.v. Lopin, A. V. TolmachevAbstract:The relationship between the Residual Porosity, linear optical loss coefficient, and sintering temperature-time regime has been studied for Y3Al5O12:Nd3+ (4 at %) laser ceramics. It is experimentally established that the linear optical loss coefficient linearly depends on the magnitude of Residual Porosity. The slope efficiency of laser generation reached a value of 31% in ceramics with a Residual Porosity on a level of 0.0016 vol % that was obtained by reactive sintering at 1750°C for 12 h. The obtained results are important for optimization of the technology of Y3Al5O12:Nd3+ laser ceramics.
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Microstructure evolution of SiO2, ZrO2-doped Y3Al5O12:Nd3+ ceramics obtained by reactive sintering
Ceramics International, 2015Co-Authors: R.p. Yavetskiy, D.yu. Kosyanov, S.v. Parkhomenko, A.g. Doroshenko, I.o. Vorona, A.v. Lopin, A. V. Tolmachev, Pavel V. Mateychenko, V.n. Baumer, V.l. VoznyyAbstract:The evolution of microstructure, Porosity and optical properties of SiO2, ZrO2-doped Y3Al5O12:Nd3+ laser ceramics obtained by reactive sintering have been studied. The relationship between the relative density and average grain size of garnet ceramics obtained in the 1500–1800 °С temperature range has been determined. It has been shown that anomalous behavior of sintering trajectory at Т>1700 °С may be due to the inhibition of ceramic grain boundaries mobility by Zr4+ ions. At the sintering temperature of 1800 °С a partial decomposition of Y3Al5O12:Nd3+, Si4+, Zr4+ solid solution occurs with precipitation of alumina along grain boundaries of ceramics. The relationships between the Residual Porosity, in-line optical transmittance and sintering conditions of Y3Al5O12:Nd3+ (4 at%) ceramics have been studied. Optical ceramics sintered at T=1750 °C for 12 h possess Residual Porosity of 0.0016 vol%, in-line optical transmittance of 82.9% at 1064 nm wavelength and laser slope efficiency of 33% under diode-pumping at 808 nm.