The Experts below are selected from a list of 123 Experts worldwide ranked by ideXlab platform
Qing Wang - One of the best experts on this subject based on the ideXlab platform.
-
colossal room temperature electrocaloric effect in ferroelectric polymer nanocomposites using nanostructured barium Strontium Titanates
ACS Nano, 2015Co-Authors: Guangzu Zhang, Tiannan Yang, Long-qing Chen, Xiaoshan Zhang, Shenglin Jiang, Qi Li, Qing WangAbstract:The electrocaloric effect (ECE) refers to conversion of thermal to electrical energy of polarizable materials and could form the basis for the next-generation refrigeration and power technologies that are highly efficient and environmentally friendly. Ferroelectric materials such as ceramic and polymer films exhibit large ECEs, but each of these monolithic materials has its own limitations for practical cooling applications. In this work, nanosized barium Strontium Titanates with systematically varied morphologies have been prepared to form polymer nanocomposites with the ferroelectric polymer matrix. The solution-processed polymer nanocomposites exhibit an extraordinary room-temperature ECE via the synergistic combination of the high breakdown strength of a ferroelectric polymer matrix and the large change of polarization with temperature of ceramic nanofillers. It is found that a sizable ECE can be generated under both modest and high electric fields, and further enhanced greatly by tailoring the morpho...
-
Colossal Roomerature Electrocaloric Effect in Ferroelectric Polymer Nanocomposites Using Nanostructured Barium Strontium Titanates
ACS Nano, 2015Co-Authors: Guangzu Zhang, Tiannan Yang, Long-qing Chen, Xiaoshan Zhang, Shenglin Jiang, Qi Li, Qing WangAbstract:The electrocaloric effect (ECE) refers to conversion of thermal to electrical energy of polarizable materials and could form the basis for the next-generation refrigeration and power technologies that are highly efficient and environmentally friendly. Ferroelectric materials such as ceramic and polymer films exhibit large ECEs, but each of these monolithic materials has its own limitations for practical cooling applications. In this work, nanosized barium Strontium Titanates with systematically varied morphologies have been prepared to form polymer nanocomposites with the ferroelectric polymer matrix. The solution-processed polymer nanocomposites exhibit an extraordinary room-temperature ECE via the synergistic combination of the high breakdown strength of a ferroelectric polymer matrix and the large change of polarization with temperature of ceramic nanofillers. It is found that a sizable ECE can be generated under both modest and high electric fields, and further enhanced greatly by tailoring the morphology of the ferroelectric nanofillers such as increasing the aspect ratio of the nanoinclusions. The effect of the geometry of the nanofillers on the dielectric permittivity, polarization, breakdown strength, ECE and crystallinity of the ferroelectric polymer has been systematically investigated. Simulations based on the phase-field model have been carried out to substantiate the experimental results. With the remarkable cooling energy density and refrigerant capacity, the polymer nanocomposites are promising for solid-state cooling applications.
Guangzu Zhang - One of the best experts on this subject based on the ideXlab platform.
-
colossal room temperature electrocaloric effect in ferroelectric polymer nanocomposites using nanostructured barium Strontium Titanates
ACS Nano, 2015Co-Authors: Guangzu Zhang, Tiannan Yang, Long-qing Chen, Xiaoshan Zhang, Shenglin Jiang, Qi Li, Qing WangAbstract:The electrocaloric effect (ECE) refers to conversion of thermal to electrical energy of polarizable materials and could form the basis for the next-generation refrigeration and power technologies that are highly efficient and environmentally friendly. Ferroelectric materials such as ceramic and polymer films exhibit large ECEs, but each of these monolithic materials has its own limitations for practical cooling applications. In this work, nanosized barium Strontium Titanates with systematically varied morphologies have been prepared to form polymer nanocomposites with the ferroelectric polymer matrix. The solution-processed polymer nanocomposites exhibit an extraordinary room-temperature ECE via the synergistic combination of the high breakdown strength of a ferroelectric polymer matrix and the large change of polarization with temperature of ceramic nanofillers. It is found that a sizable ECE can be generated under both modest and high electric fields, and further enhanced greatly by tailoring the morpho...
-
Colossal Roomerature Electrocaloric Effect in Ferroelectric Polymer Nanocomposites Using Nanostructured Barium Strontium Titanates
ACS Nano, 2015Co-Authors: Guangzu Zhang, Tiannan Yang, Long-qing Chen, Xiaoshan Zhang, Shenglin Jiang, Qi Li, Qing WangAbstract:The electrocaloric effect (ECE) refers to conversion of thermal to electrical energy of polarizable materials and could form the basis for the next-generation refrigeration and power technologies that are highly efficient and environmentally friendly. Ferroelectric materials such as ceramic and polymer films exhibit large ECEs, but each of these monolithic materials has its own limitations for practical cooling applications. In this work, nanosized barium Strontium Titanates with systematically varied morphologies have been prepared to form polymer nanocomposites with the ferroelectric polymer matrix. The solution-processed polymer nanocomposites exhibit an extraordinary room-temperature ECE via the synergistic combination of the high breakdown strength of a ferroelectric polymer matrix and the large change of polarization with temperature of ceramic nanofillers. It is found that a sizable ECE can be generated under both modest and high electric fields, and further enhanced greatly by tailoring the morphology of the ferroelectric nanofillers such as increasing the aspect ratio of the nanoinclusions. The effect of the geometry of the nanofillers on the dielectric permittivity, polarization, breakdown strength, ECE and crystallinity of the ferroelectric polymer has been systematically investigated. Simulations based on the phase-field model have been carried out to substantiate the experimental results. With the remarkable cooling energy density and refrigerant capacity, the polymer nanocomposites are promising for solid-state cooling applications.
Arun Majumdar - One of the best experts on this subject based on the ideXlab platform.
-
thermal conductivity reduction in oxygen deficient Strontium Titanates
Applied Physics Letters, 2008Co-Authors: Choongho Yu, Matthew L Scullin, Mark Huijben, R Ramesh, Arun MajumdarAbstract:We report significant thermal conductivity reduction in oxygen-deficient lanthanum-doped Strontium titanate (Sr1−xLaxTiO3−δ) films as compared to unreduced Strontium Titanates. Our experimental results suggest that the oxygen vacancies could have played an important role in the reduction. This could be due to the nature of randomly distributed and clustered vacancies, which would be very effective to scatter phonons. Our results could provide a pathway for tailoring the thermal conductivity of complex oxides, which is very beneficial to various applications including thermoelectrics
-
the influence of oxygen deficiency on the thermoelectric properties of Strontium Titanates
Applied Physics Letters, 2008Co-Authors: Choongho Yu, Matthew L Scullin, Mark Huijben, R Ramesh, Arun MajumdarAbstract:We report oxygen reduction in bulk Strontium titanate substrates when a thin film was deposited in an oxygen-deficient environment. The oxygen diffusion occurred at moderate temperatures and oxygen pressures, which were not enough to produce detectable oxygen vacancies without the film deposition. In order to identify the reduction, we used a series of different annealing conditions and various substrates and performed comparative studies regarding thermoelectric properties before and after removing the films. Our experimental results suggest that the measurements of material properties of thin films on SrTiO3 single crystal substrates need to be performed carefully due to its strong susceptibility to oxygen deficient conditions
Choongho Yu - One of the best experts on this subject based on the ideXlab platform.
-
a simple synthesis of long nanostructured arrays of crystalline Strontium Titanates at low temperatures
Journal of Materials Science, 2011Co-Authors: Yunki Gwak, Choongho YuAbstract:Long aligned arrays of crystalline Strontium titanate (SrTiO3) nanostructures were synthesized by using simple low-temperature processes that incorporate Strontium into titanium oxides. Tubular nanostructures are often confine energy carriers that result in extraordinary transport behaviors in various semiconductors including Strontium Titanates, which are promising for developing efficient thermoelectric energy conversion materials. However, synthesizing a micron-to-milimeter scale array of one-dimensional ternary nanostructures has been difficult. Moreover, ternary compounds are often obtained as disordered cubic-shape particles at the end of complicated and/or long reactions. In this study, a two-step process—anodization for preparing amorphous titanium oxides and a subsequent thermal annealing process in a mixture of Strontium hydroxide, ammonia, and water—was employed. Typical diameter and length of the tubes are ~150 nm and ~160 μm, respectively. It has been found that the amorphous structure of titanium oxides plays an important role in obtaining high-purity long Strontium titanate nanotubes at low temperatures (90 and 180 °C) with short reaction times. Comparative and systematic studies with different sample pre-treatments, etching times, temperatures, reaction times, and Strontium concentrations revealed reaction mechanisms and key synthesis parameters, which may be utilized to obtain other ternary or quaternary nanostructured compounds such as barium or lead Titanates.
-
thermal conductivity reduction in oxygen deficient Strontium Titanates
Applied Physics Letters, 2008Co-Authors: Choongho Yu, Matthew L Scullin, Mark Huijben, R Ramesh, Arun MajumdarAbstract:We report significant thermal conductivity reduction in oxygen-deficient lanthanum-doped Strontium titanate (Sr1−xLaxTiO3−δ) films as compared to unreduced Strontium Titanates. Our experimental results suggest that the oxygen vacancies could have played an important role in the reduction. This could be due to the nature of randomly distributed and clustered vacancies, which would be very effective to scatter phonons. Our results could provide a pathway for tailoring the thermal conductivity of complex oxides, which is very beneficial to various applications including thermoelectrics
-
the influence of oxygen deficiency on the thermoelectric properties of Strontium Titanates
Applied Physics Letters, 2008Co-Authors: Choongho Yu, Matthew L Scullin, Mark Huijben, R Ramesh, Arun MajumdarAbstract:We report oxygen reduction in bulk Strontium titanate substrates when a thin film was deposited in an oxygen-deficient environment. The oxygen diffusion occurred at moderate temperatures and oxygen pressures, which were not enough to produce detectable oxygen vacancies without the film deposition. In order to identify the reduction, we used a series of different annealing conditions and various substrates and performed comparative studies regarding thermoelectric properties before and after removing the films. Our experimental results suggest that the measurements of material properties of thin films on SrTiO3 single crystal substrates need to be performed carefully due to its strong susceptibility to oxygen deficient conditions
Jongshik Chung - One of the best experts on this subject based on the ideXlab platform.
-
ru doped barium Strontium Titanates of the cathode for the electrochemical synthesis of ammonia
Solid State Ionics, 2019Co-Authors: Yong Sik Chung, Heechul Yoon, Jae Gi Sung, Han Kyu Jung, Lauren Beverly Sammes, Jongshik ChungAbstract:Abstract Ru-doped barium Strontium titanate (BSTR) perovskites (Ba0.5Sr0.5Ti1-xRuxO3-δ, x = 0, 0.05, 0.1) (BSTR) were evaluated as cathode materials for the electrochemical synthesis of ammonia from wet H2 and dry N2. Phase crystallinity and the electrochemical properties of BSTR were analyzed. The BSTR structure is stable in low oxygen partial pressure, possibly as a result of its cubic nature. Doping Ru on the B-site of the BST improves its electrochemical properties, because increasing replacement of Ti4+ by Ru4+ causes a decrease in ohmic resistance. Introduction of Ru4+ ions on the B-site of the BST increased catalytic activity for the ammonia synthesis reaction. An electrochemical cell using BSTR as the cathode (Ni/BaCe0.4Zr0.4Y0.2O3 (BCZY)/BCZY/BSTR) exhibits a maximum ammonia formation rate of 1.1 × 10−9 mol s−1 cm−2 and a Faradaic efficiency of 5.9% at 500 °C under an applied voltage of 1.2 V; short-term stability tests showed high stability.
-
ru doped lanthanum Strontium Titanates for the anode of solid oxide fuel cells
International Journal of Hydrogen Energy, 2015Co-Authors: Heechul Yoon, Nigel Sammes, Jongshik ChungAbstract:Abstract Lanthanum Strontium titanate perovskite (LST) was doped with Ru (La 0.4 Sr 0.6 Ti 1−x Ru x O 3−δ (LSTR), x = 0.02, 0.05), and its properties were characterized by various methods for possible use as the anode material in solid oxide fuel cells (SOFCs). The thermal expansion coefficients of Ru-doped samples (10.2–10.3 × 10 −6 K −1 ) are about the same as LST (10.4 × 10 −6 K −1 ), which is similar to that of YSZ. It has been found that under a reducing atmosphere, doped Ru is precipitated from the structure. This decreases the total electrical conductivity and increases the ionic conductivity because of the increased number of B-site deficiencies created by the Ru precipitation. Impedance spectra measured with the buttons cells of the LSTRs-YSZ/YSZ/LSM-YSZ/LSM configuration reveal that the polarization resistance with the LST–YSZ anode increases with time (from 4.95 Ω cm 2 to 5.78 Ω cm 2 in 24 h of H 2 fuel atmosphere), whereas the resistance with Ru-doped LST–YSZ anodes decreases with time (from 4.87 Ω cm 2 and 4.17 Ω cm 2 to 4.06 Ω cm 2 and 2.74 Ω cm 2 for the LSTR0.02-YSZ and LSTR0.05-YSZ anodes, respectively). Accordingly, the final maximum power density at 850 °C also increases from 52 mW/cm 2 for LST–YSZ to 74 mW/cm 2 and 115 mW/cm 2 for the LSTR0.02-YSZ and LSTR0.05-YSZ anodes, respectively.
