The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform
C Panagopoulos - One of the best experts on this subject based on the ideXlab platform.
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role of intrinsic disorder in the structural phase transition of magnetoelectric eutio 3
Physical Review B, 2012Co-Authors: Mattia Allieta, Marco Scavini, Leszek J Spalek, V Scagnoli, H C Walker, C Panagopoulos, S S Saxena, Takuro KatsufujiAbstract:Up to now, the crystallographic structure of the magnetoelectric perovskite EuTiO${}_{3}$ has been considered to remain cubic down to low temperature. Here we present high-resolution synchrotron x-ray powder-diffraction data showing the existence of a structural phase transition, from cubic $Pm$-3$m$ to tetragonal $I4\text{/}mcm$, involving TiO${}_{6}$ octahedra tilting, in analogy to the case of SrTiO${}_{3}$. The temperature evolution of the tilting angle and of the full width at half maximum of the (200) cubic reflection family indicate a critical temperature ${T}_{c}$ $=$ 235 K. This critical temperature is well below the recent anomaly reported by specific-Heat Measurement at ${T}_{A}$ \ensuremath{\sim} 282 K. By performing atomic pair distribution function analysis on diffraction data, we provide evidence of a mismatch between the local (short-range) and the average crystallographic structures in this material. Below the estimated ${T}_{c}$, the average model symmetry is fully compatible with the local environment distortion, but the former is characterized by a reduced value of the tilting angle compared to the latter. At $T$ $=$ 240 K, data show the presence of local octahedra tilting identical to the low-temperature one, while the average crystallographic structure remains cubic. On this basis, we propose that intrinsic lattice disorder is of fundamental importance in the understanding of EuTiO${}_{3}$ properties.
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role of intrinsic disorder in the structural phase transition of magnetoelectric eutio3
Physical Review B, 2012Co-Authors: Mattia Allieta, Marco Scavini, Leszek J Spalek, V Scagnoli, H C Walker, C PanagopoulosAbstract:Up to now the crystallographic structure of the magnetoelectric perovskite EuTiO3 was considered to remain cubic down to low temperature. Here we present high resolution synchrotron X-ray powder diffraction data showing the existence of a structural phase transition, from cubic Pm-3m to tetragonal I4/mcm, involving TiO6 octahedra tilting, in analogy to the case of SrTiO3. The temperature evolution of the tilting angle indicates a second-order phase transition with an estimated Tc=235K. This critical temperature is well below the recent anomaly reported by specific Heat Measurement at TA\sim282K. By performing atomic pair distribution function analysis on diffraction data we provide evidence of a mismatch between the local (short-range) and the average crystallographic structures in this material. Below the estimated Tc, the average model symmetry is fully compatible with the local environment distortion but the former is characterized by a reduced value of the tilting angle compared to the latter. At T=240K data show the presence of local octahedra tilting identical to the low temperature one, while the average crystallographic structure remains cubic. On this basis, we propose intrinsic lattice disorder to be of fundamental importance in the understanding of EuTiO3 properties.
Shin-ichi Sasa - One of the best experts on this subject based on the ideXlab platform.
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Possible extended forms of thermodynamic entropy
Journal of Statistical Mechanics: Theory and Experiment, 2014Co-Authors: Shin-ichi SasaAbstract:Thermodynamic entropy is determined by a Heat Measurement through the Clausius equality. The entropy then formalizes a fundamental limitation of operations by the second law of thermodynamics. The entropy is also expressed as the Shannon entropy of the microscopic degrees of freedom. Whenever an extension of thermodynamic entropy is attempted, we must pay special attention to how its three different aspects just mentioned are altered. In this paper, we discuss possible extensions of the thermodynamic entropy.
Nobuhisa Kaneko - One of the best experts on this subject based on the ideXlab platform.
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High-accuracy compensation of radiative Heat loss in Thomson coefficient Measurement
Applied Physics Letters, 2020Co-Authors: Takeshi Shimazaki, Kenjiro Okawa, Tatsuya Kawae, Nobuhisa KanekoAbstract:We report a simple and accurate method to address the inevitable radiative Heat loss in the Thomson coefficient Measurement. The additional steps required are the Measurement of the Joule Heat arising from the ac current, Measurement of the electrical resistance of the sample, and calculation of the ratio of the two Measurement signals arising from the Joule and Thomson effects. The underlying concept is that most of the radiative Heat loss that occurs during the Measurement of Joule and Thomson Heats can be compensated for by calculating the ratio of the two signals. This is because the Heat loss during the Joule Heat Measurement will be highly similar to that during the Thomson Heat Measurement. Heat transfer analysis indicates that radiative Heat loss is reduced by at least a factor of six. Once the Thomson coefficient is measured, accurate Seebeck and Peltier coefficients can be obtained in a single run. This approach was demonstrated by performing Measurements on fine platinum wires in the temperature range of 80 K–300 K. The difference between the compensated and uncompensated curves became significant as the temperature increased; moreover, this difference was proportional to the cube of the temperature for a long fine-wire sample, where there is substantial radiative Heat loss. Thus, the proposed approach is completely different from a conventional one, wherein the Measurement accuracy degrades owing to inevitable radiative Heat loss without prior knowledge of the thermal conductivity and emissivity of the sample.
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Analysis of Heat loss for Measurement of Thomson coefficient using AC calorimetric method
2016 Conference on Precision Electromagnetic Measurements (CPEM 2016), 2016Co-Authors: Takeshi Shimazaki, Atsushi Yamamoto, Nobuhisa KanekoAbstract:We introduce an AC calorimetric technique to measure absolute Seebeck coefficient for thermoelectric metrology. The Measurement of Thomson Heat can only determine the Seebeck coefficient of single materials using Kelvin relation. Our Heat transfer analysis in the Thomson Heat Measurement indicates that the use of AC current can compensate for the Heat loss from the thermocouple, which is inevitable Heat transfer in a contact temperature Measurement. Experimental results nicely reproduce those predicted by the Heat transfer analysis. Our AC calorimetric method allows us to perform accurate and simple Measurements without considering the effect of Heat loss.
V Scagnoli - One of the best experts on this subject based on the ideXlab platform.
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role of intrinsic disorder in the structural phase transition of magnetoelectric eutio 3
Physical Review B, 2012Co-Authors: Mattia Allieta, Marco Scavini, Leszek J Spalek, V Scagnoli, H C Walker, C Panagopoulos, S S Saxena, Takuro KatsufujiAbstract:Up to now, the crystallographic structure of the magnetoelectric perovskite EuTiO${}_{3}$ has been considered to remain cubic down to low temperature. Here we present high-resolution synchrotron x-ray powder-diffraction data showing the existence of a structural phase transition, from cubic $Pm$-3$m$ to tetragonal $I4\text{/}mcm$, involving TiO${}_{6}$ octahedra tilting, in analogy to the case of SrTiO${}_{3}$. The temperature evolution of the tilting angle and of the full width at half maximum of the (200) cubic reflection family indicate a critical temperature ${T}_{c}$ $=$ 235 K. This critical temperature is well below the recent anomaly reported by specific-Heat Measurement at ${T}_{A}$ \ensuremath{\sim} 282 K. By performing atomic pair distribution function analysis on diffraction data, we provide evidence of a mismatch between the local (short-range) and the average crystallographic structures in this material. Below the estimated ${T}_{c}$, the average model symmetry is fully compatible with the local environment distortion, but the former is characterized by a reduced value of the tilting angle compared to the latter. At $T$ $=$ 240 K, data show the presence of local octahedra tilting identical to the low-temperature one, while the average crystallographic structure remains cubic. On this basis, we propose that intrinsic lattice disorder is of fundamental importance in the understanding of EuTiO${}_{3}$ properties.
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role of intrinsic disorder in the structural phase transition of magnetoelectric eutio3
Physical Review B, 2012Co-Authors: Mattia Allieta, Marco Scavini, Leszek J Spalek, V Scagnoli, H C Walker, C PanagopoulosAbstract:Up to now the crystallographic structure of the magnetoelectric perovskite EuTiO3 was considered to remain cubic down to low temperature. Here we present high resolution synchrotron X-ray powder diffraction data showing the existence of a structural phase transition, from cubic Pm-3m to tetragonal I4/mcm, involving TiO6 octahedra tilting, in analogy to the case of SrTiO3. The temperature evolution of the tilting angle indicates a second-order phase transition with an estimated Tc=235K. This critical temperature is well below the recent anomaly reported by specific Heat Measurement at TA\sim282K. By performing atomic pair distribution function analysis on diffraction data we provide evidence of a mismatch between the local (short-range) and the average crystallographic structures in this material. Below the estimated Tc, the average model symmetry is fully compatible with the local environment distortion but the former is characterized by a reduced value of the tilting angle compared to the latter. At T=240K data show the presence of local octahedra tilting identical to the low temperature one, while the average crystallographic structure remains cubic. On this basis, we propose intrinsic lattice disorder to be of fundamental importance in the understanding of EuTiO3 properties.
Walter Eysel - One of the best experts on this subject based on the ideXlab platform.
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the caloric calibration of scanning calorimeters
Thermochimica Acta, 1994Co-Authors: Stefan M Sarge, E Gmelin, G W H Hohne, H K Cammenga, Wolfgang F Hemminger, Walter EyselAbstract:Abstract The present recommendation of the GEFTA working group “Calibration of Scanning Calorimeters” allows a precise Heat and Heat flow rate calibration of scanning calorimeters, largely independent of instrumental, sample-related and experimental parameters. Electric energy, electric power, Heats of transition and Heat capacities of suitable calibration substances are used for calibration. The measuring method, measuring and evaluation procedure, calibration materials, significant influencing factors, sources of error and detailed examples are presented for these calibration methods. Besides specific problems of Heat Measurement (interpolation of the baseline for the peak area determination) and Heat capacity Measurement (interpolation between initial and final isotherms, determination of the true Heating rate of the sample, thermal lag of the sample), general aspects (thermodynamic fundamentals, difference between Heat and Heat flow rate calibration factor, weighing procedure) are also discussed.
