Microstructure dynamics in orthorhombic perovskites

Zhang, Zhiying; Koppensteiner, J.; Schranz, W.; Betts, J. B.; Migliori, A.; Carpenter, Michael A.

doi:10.1103/physrevb.82.014113

Cited by 61 publications

(89 citation statements)

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“…[42][43][44] At low temperature, the structure is orthorhombic with space group Pnma (a − b + a − using Glazer's notations 14 ), as already explained. When heating, it first loses the in-phase tilt to turn into the I mma space group (a − b 0 a − ) around 550 K. Then the structure changes through a first-order transition at 670 K to a rhombohedral phase with space group R3c (a − a − a − ).…”

Section: A Baceomentioning

confidence: 99%

Thermodynamics of hydration and oxidation in the proton conductor Gd-doped barium cerate from density functional theory calculations

et al. 2012

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Hydration and oxidation of gadolinium-doped barium cerate, a system with highly promising properties when used as electrolyte for protonic ceramic fuel cells, are investigated by means of density functional calculations. The energy landscape of oxygen vacancies and interstitial protons in this strongly distorted orthorhombic perovskite is computed. Although the most stable sites for protons are found in the close vicinity of the dopant, the picture of a very complex energy landscape emerges, in which some sites far away from Gd are found more stable than other ones in its close vicinity, due to the highly distorted geometry of the host materials. The fully hydrated phase can be approximated by a structure with 16 local minima. Both hydration (water incorporation) and oxidation (oxygen incorporation) are found to be exothermic processes with reaction enthalpies of −1.34 eV/H 2 O molecule and −0.70 eV/O atom, respectively. The hole polaron resulting from the exothermic incorporation of oxygen is found localized on oxygens around the dopant (small polaron) and carries a spin magnetic moment. Finally, the competition between hydration and oxidation is studied and discussed as a function of oxygen and water partial pressures.

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Section: A Baceomentioning

confidence: 99%

Thermodynamics of hydration and oxidation in the proton conductor Gd-doped barium cerate from density functional theory calculations

et al. 2012

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“…Some softening is almost invariably observed, however, and is attributed to dynamical effects. The interval of premonitory softening is less than ∼50 K for octahedral tilting transitions, as in KMnF 3 [59], SrTiO 3 [23], SrZrO 3 [39], BaCeO 3 [60] and LaAlO 3 [43], for example, but extends to ∼200-300 K for ferroelectric and relaxor-ferroelectric phases, such as BaTiO 3 [61,62] [65,66]. From the present study, the same softening interval is 500 K in NdCo 2 and ∼125 K in ErCo 2 , and its form has the potential for providing some understanding of the nature of precursor ordering effects in magnetic systems.…”

Section: Softening Mechanisms In the Stability Range Of The Cubic Phasesmentioning

confidence: 99%

Multiferroic (ferroelastic/ferromagnetic/ferrimagnetic) aspects of phase transitions in RCo₂Laves phases

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Herrero‐Albillos

Bonilla

et al. 2014

J. Phys.: Condens. Matter

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Magnetic phase transitions in RCo 2 Laves phases with R as a rare earth element are accompanied by changes in crystallographic space group. For purely structural transitions they would be described as improper ferroelastic and therefore fulfil the condition for multiferroic phase transitions in combining two out of three properties, ferro/antiferromagnetism, ferroelectricity and ferroelasticity. Here lattice parameter data from the literature and new measurements of elastic and anelastic properties, by resonant ultrasound spectroscopy, for NdCo 2 and ErCo 2 have been analysed from this perspective. The temperature dependence of symmetry-breaking shear strains is consistent with the cubic ↔ tetragonal transition in NdCo 2 being close to tricritical in character and the cubic ↔ rhombohedral transition in ErCo 2 being first order. Elastic softening and acoustic loss within the stability ranges of the ferroelastic phases can be understood in terms of a combination of intrinsic softening due to strain/order parameter coupling and ferroelastic twin-wall motion. Softening ahead of the transitions does not fit with standard macroscopic descriptions of dynamic effects from other systems but, rather, in the case of NdCo 2 , might be attributed to the involvement of a second zone centre order parameter related to a separate instability driven by cooperative Jahn-Teller distortions. In ErCo 2 , acoustic loss in the temperature interval above the transition point is discussed in terms of a possible tweed microstructure associated with strain coupling to local magnetic ordering. The overall multiferroic behaviour can be understood in terms of a single magnetic order parameter (irrep m + 4 of magnetic space group Fd3m1 ) which couples with a structural order parameter (irrep + 3 or + 5 ). The coupling is linear/quadratic which, in the case of two separate instabilities, causes them to combine in a single multiferroic phase transition.

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“…From considerations of the phase diagram, the pattern is expected to be that of a tricritical transition. The steep and nonlinear stiffening with falling temperature below T c is characteristic of tricritical character, as seen, for example, in association with tilting transitions in SrZrO 3 [129], KMnF 3 [130,131], BaCeO 3 [132] and quartz [125]. Also as expected in this context, there is a correlation between the magnitudes of the reduction in f 2 , measuring softening of the shear modulus, and the magnitudes of the tetragonal shear strains.…”

Section: Improper Ferroelastic Transitionmentioning

confidence: 56%

Elastic and anelastic relaxation behaviour of perovskite multiferroics I: PbZr0.53Ti0.47O3 (PZT)–PbFe0.5Nb0.5O3 (PFN)

et al. 2016

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Perovskites in the ternary system PbTiO 3 (PT)-PbZrO 3 (PZ)-Pb(Fe 0.5 Nb 0.5 )O 3 (PFN) have attracted close interest because they can display simultaneous ferroelectric, magnetic and ferroelastic properties. Those with the most sensitive response to external fields are likely to have compositions near the morphotropic phase boundary (MPB) which lies close to the binary join Pb(Zr 0.53 Ti 0.47 )O 3 (PZT)-PFN. In the present study, the strength and dynamics of strain coupling behaviour which accompanies the development of ferroelectricity and (anti)ferromagnetism in ceramic PZT-PFN samples have been investigated by resonant ultrasound spectroscopy. Elastic softening ahead of the cubic-tetragonal transition does not fit with models based on dispersion of the soft mode or relaxor characteristics but is attributed, instead, to coupling between acoustic modes and a central peak mode from correlated relaxations and/or microstructure dynamics. Softening of the shear modulus through the transition by up to *50 % fits with the expected pattern for linear/quadratic strain/order parameter coupling at an improper ferroelastic transition and close to tricritical evolution for the order parameter. Superattenuation of acoustic resonances in a temperature interval of *100 K below the transition point is indicative of mobile ferroelastic twin walls. By way of contrast, the first-order tetragonalmonoclinic transition involves only a small change in the shear modulus and is not accompanied by significant changes in acoustic dissipation. The dominant Address correspondence to E-mail: mc43@esc.cam.ac.uk DOI 10.1007/s10853-016-0280-2 J Mater Sci (2016) 51:10727-10760 feature of the elastic and anelastic properties at low temperatures is a concaveup variation of the shear modulus and relatively high loss down to the lowest temperature, which appears to be the signature of materials with substantial local strain heterogeneity and a spectrum of strain relaxation times. No evidence of magnetoelastic coupling has been found, in spite of the samples displaying ferromagnetism below *550 K and possible spin glass ordering below *50 K. For the important multiferroic perovskite ceramics with compositions close to the MPB of ternary PT-PZ-PFN, there must be some focus in future on the role of strain heterogeneity.

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Microstructure dynamics in orthorhombic perovskites

Cited by 61 publications

References 50 publications

Thermodynamics of hydration and oxidation in the proton conductor Gd-doped barium cerate from density functional theory calculations

Thermodynamics of hydration and oxidation in the proton conductor Gd-doped barium cerate from density functional theory calculations

Multiferroic (ferroelastic/ferromagnetic/ferrimagnetic) aspects of phase transitions in RCo₂Laves phases

Elastic and anelastic relaxation behaviour of perovskite multiferroics I: PbZr0.53Ti0.47O3 (PZT)–PbFe0.5Nb0.5O3 (PFN)

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Microstructure dynamics in orthorhombic perovskites

Cited by 61 publications

References 50 publications

Thermodynamics of hydration and oxidation in the proton conductor Gd-doped barium cerate from density functional theory calculations

Thermodynamics of hydration and oxidation in the proton conductor Gd-doped barium cerate from density functional theory calculations

Multiferroic (ferroelastic/ferromagnetic/ferrimagnetic) aspects of phase transitions in RCo2Laves phases

Elastic and anelastic relaxation behaviour of perovskite multiferroics I: PbZr0.53Ti0.47O3 (PZT)–PbFe0.5Nb0.5O3 (PFN)

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Multiferroic (ferroelastic/ferromagnetic/ferrimagnetic) aspects of phase transitions in RCo₂Laves phases