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Dynamic processes of domain switching in lead zirconate titanate under cyclic mechanical loading by in situ neutron diffraction / Soodkhet Pojprapai(Imlao) in Acta materialia, Vol. 58 N° 6 (Avril 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 6 (Avril 2010) . - pp. 1897–1908 Titre : Dynamic processes of domain switching in lead zirconate titanate under cyclic mechanical loading by in situ neutron diffraction Type de document : texte imprimé Auteurs : Soodkhet Pojprapai(Imlao), Auteur ; Zhenhua Luo, Auteur ; Bjørn Clausen, Auteur Année de publication : 2011 Article en page(s) : pp. 1897–1908 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Ferroelectric  Ferroelastic  Domain  switching  Neutron  diffraction Résumé : The performance of ferroelectric ceramics is governed by the ability of domains to switch. A decrease in the switching ability can lead to degradation of the materials and failure of ferroelectric devices. In this work the dynamic properties of domain reorientation are studied. In situ time-of-flight neutron diffraction is used to probe the evolution of ferroelastic domain texture under mechanical cyclic loading in bulk lead zirconate titanate ceramics. The high sensitivity of neutron diffraction to lattice strain is exploited to precisely analyze the change of domain texture and strain through a full-pattern Rietveld method. These results are then used to construct a viscoelastic model, which explains the correlation between macroscopic phenomena (i.e. creep and recovered deformation) and microscopic dynamic behavior (i.e. ferroelastic switching, lattice strain). DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409008052 [article] Dynamic processes of domain switching in lead zirconate titanate under cyclic mechanical loading by in situ neutron diffraction [texte imprimé] / Soodkhet Pojprapai(Imlao), Auteur ; Zhenhua Luo, Auteur ; Bjørn Clausen, Auteur . - 2011 . - pp. 1897–1908. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 6 (Avril 2010) . - pp. 1897–1908 Mots-clés : Ferroelectric  Ferroelastic  Domain  switching  Neutron  diffraction Résumé : The performance of ferroelectric ceramics is governed by the ability of domains to switch. A decrease in the switching ability can lead to degradation of the materials and failure of ferroelectric devices. In this work the dynamic properties of domain reorientation are studied. In situ time-of-flight neutron diffraction is used to probe the evolution of ferroelastic domain texture under mechanical cyclic loading in bulk lead zirconate titanate ceramics. The high sensitivity of neutron diffraction to lattice strain is exploited to precisely analyze the change of domain texture and strain through a full-pattern Rietveld method. These results are then used to construct a viscoelastic model, which explains the correlation between macroscopic phenomena (i.e. creep and recovered deformation) and microscopic dynamic behavior (i.e. ferroelastic switching, lattice strain). DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409008052

On the stress-free lattice expansion of porous cordierite / Giovanni Bruno in Acta materialia, Vol. 58 N° 6 (Avril 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 6 (Avril 2010) . - pp. 1994–2003 Titre : On the stress-free lattice expansion of porous cordierite Type de document : texte imprimé Auteurs : Giovanni Bruno, Auteur ; Alexander M. Efremov, Auteur ; Bjørn Clausen, Auteur Année de publication : 2011 Article en page(s) : pp. 1994–2003 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Micro-strains  Neutron  diffraction  Thermal  expansion  Integrity  factor  Micro-cracking Résumé : An extensive investigation of the lattice expansion (up to 1200 °C) of porous synthetic cordierite (obtained by firing a mixture of talc, clay, alumina and silica) was carried out using time-of-flight neutron diffraction at LANSCE, Los Alamos, NM, USA and FNLP, Dubna, Russia. An extruded rod and several powders, with different particle size (dispersity), were studied, with the aim of monitoring the variation of the (lattice) micro-strain as a function of temperature and its influence on the microscopic and macroscopic thermal expansion. Results show a different expansion of the a- and b-axes of the orthorhombic cell (in the rod above 800 °C). While the finest powder seems to contract more along the c-axis, thus hinting at the presence of smaller stress, the integral peak width increases as a function of temperature in the intermediate range (300–700 °C). This could be explained by the integrity factor modeling in terms of micro-cracking. In polycrystalline cordierite, the model implies tension along the a- and b-axes (positive thermal expansion) accompanied by compression along the c-axis (negative thermal expansion) and a stress release upon cooling, via a thermal micro-cracking mechanism. The calculations of the cordierite macroscopic thermal expansion having as input crystal axial expansions assumed to be stress-free allowed us to conclude that even a fine powder (5 μm particle size) cannot be considered completely stress-free. This conclusion is supported by microstructural observations. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409008210 [article] On the stress-free lattice expansion of porous cordierite [texte imprimé] / Giovanni Bruno, Auteur ; Alexander M. Efremov, Auteur ; Bjørn Clausen, Auteur . - 2011 . - pp. 1994–2003. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 6 (Avril 2010) . - pp. 1994–2003 Mots-clés : Micro-strains  Neutron  diffraction  Thermal  expansion  Integrity  factor  Micro-cracking Résumé : An extensive investigation of the lattice expansion (up to 1200 °C) of porous synthetic cordierite (obtained by firing a mixture of talc, clay, alumina and silica) was carried out using time-of-flight neutron diffraction at LANSCE, Los Alamos, NM, USA and FNLP, Dubna, Russia. An extruded rod and several powders, with different particle size (dispersity), were studied, with the aim of monitoring the variation of the (lattice) micro-strain as a function of temperature and its influence on the microscopic and macroscopic thermal expansion. Results show a different expansion of the a- and b-axes of the orthorhombic cell (in the rod above 800 °C). While the finest powder seems to contract more along the c-axis, thus hinting at the presence of smaller stress, the integral peak width increases as a function of temperature in the intermediate range (300–700 °C). This could be explained by the integrity factor modeling in terms of micro-cracking. In polycrystalline cordierite, the model implies tension along the a- and b-axes (positive thermal expansion) accompanied by compression along the c-axis (negative thermal expansion) and a stress release upon cooling, via a thermal micro-cracking mechanism. The calculations of the cordierite macroscopic thermal expansion having as input crystal axial expansions assumed to be stress-free allowed us to conclude that even a fine powder (5 μm particle size) cannot be considered completely stress-free. This conclusion is supported by microstructural observations. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409008210