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Cordero, F.; Craciun, F.; Trequattrini, F.; Galassi, Carmen

doi:10.1103/physrevb.93.174111

Cited by 21 publications

(25 citation statements)

References 26 publications

(50 reference statements)

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“…(1) relies on the assumption that the depolarization field is negligible, a condition that it is argued to be approximated for unpoled samples probed by vibrations whose wavelength exceed the domain size. [36][37][38] There is however no quantitative assessment in this sense yet, and it cannot be excluded that at the present conditions E dep partially restrains the piezoelectric softening in the absence of free charges. In this case, the charge carriers introduced by doping would neutralize the polarization charges and the associated E dep , resulting in an enhancement of the observed piezoelectric softening.…”

Section: B Interpretation Of the Elastic Anomalies In Batio 3−δ As Pmentioning

confidence: 82%

Probing ferroelectricity in highly conducting materials through their elastic response: Persistence of ferroelectricity in metallic BaTiO3−δ

et al. 2019

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The question whether ferroelectricity (FE) may coexist with a metallic or highly conducting state, or rather it must be suppressed by the screening from the free charges, is the focus of a rapidly increasing number of theoretical studies and is finally receiving positive experimental responses. The issue is closely related to the thermoelectric and multiferroic (also magnetic) applications of FE materials, where the electrical conductivity is required or spurious. In these circumstances, the traditional methods for probing ferroelectricity are hampered or made totally ineffective by the free charges, which screen the polar response to an external electric field. This fact may explain why more than 40 years passed between the first proposals of FE metals and the present experimental and theoretical activity. The measurement of the elastic moduli, Young's modulus in the present case, versus temperature is an effective method for studying the influence of doping on a FE transition because the elastic properties are unaffected by electrical conductivity. In this manner, it is shown that the FE transitions of BaTiO 3−δ are not suppressed by electron doping through O vacancies; only the onset temperatures are depressed, but the magnitudes of the softenings, and hence of the piezoelectric activity, are initially even increased.

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Section: B Interpretation Of the Elastic Anomalies In Batio 3−δ As Pmentioning

confidence: 82%

Probing ferroelectricity in highly conducting materials through their elastic response: Persistence of ferroelectricity in metallic BaTiO3−δ

et al. 2019

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“…The two anomalies at the tilt transitions consist of steplike softenings on cooling, and hence stiffenings during heating, as observed in Figure 7. Instead, the step of opposite sign, which is clearly visible during all heatings and many coolings, is identified with the polar AFE mode, based on the fact that in the FE phase there is a piezoelectric softening [13], which disappears together with the piezoelectric constants in the AFE phase. Initially we exchanged the assignments of the steps from the OT and AF modes [44,45], because we had not yet recognized the importance of the piezoelectric softening, but those fits are valid with minimal changes in the parameters and exchanging the assignments OT and AF.…”

Section: Aging and Recovery Of Pzt Undergoing Fe/afe Transitionsmentioning

confidence: 99%

Ionic Mobility and Phase Transitions in Perovskite Oxides for Energy Application

2017

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Perovskite oxides find applications or are studied in many fields related to energy production, accumulation and saving. The most obvious application is oxygen or proton conductors in fuel cells (SOFCs), but the (anti)ferroelectric compositions may find application in high energy capacitors for energy storage, efficient electrocaloric cooling, and electromechanical energy harvesting. In SOFCs, the diffusion of O vacancies and other mobile ionic species, such as H + , are at the base of the functioning of the device, while in the other cases they constitute unwanted defects that reduce the performance and life-time of the device. Similarly, the (anti)ferroelectric phase transitions are a requisite for the use of some types of devices, but the accompanying domain walls can generate extended defects detrimental to the life of the material, and structural phase transformations should be avoided in SOFCs. All these phenomena can be studied by mechanical spectroscopy, the measurement of the complex elastic compliance as a function of temperature and frequency, which is the mechanical analogue of the dielectric susceptibility, but probes the elastic response and elastic dipoles instead of the dielectric response and electric dipoles. The two techniques can be combined to provide a comprehensive picture of the material properties. Examples are shown of the study of structural transitions and hopping and tunneling processes of O vacancies and H in the ion conductor BaCe 1−x Y x O 3−x and in SrTiO 3−x , and of the aging and fatigue effects found in PZT at compositions where the ferro-and antiferroelectric states coexist.

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“…In addition, the elastic response of the intermediate phase between T AF and T C has changed, as put in evidence in Fig. 4; here the s ′ heating curves of undoped and La doped PZT are compared and the dashed region corresponds to the piezoelectric softening 22 within the FE phase of PZT, totally absent in PLZT, so that even the sign of the step at T AF has changed.…”

Section: Introductionmentioning

confidence: 96%

“…In undoped PZT, when cooling from the PE phase one finds a very extended precursor softening ending in a spike at T C and the compliance remains larger (or the modulus softer) in the FE phase. The softening in the FE phase is of piezoelectric origin 22 , and is therefore absent in the AFE phase. In fact, in Fig.…”

Section: Fig 7 Volumes Of the Pseudocubic Unit Cells R-fe (R3m) O-mentioning

confidence: 99%

Elastic aging from coexistence and transformations of ferroelectric and antiferroelectric states in PZT

Cordero

Craciun

Trequattrini

et al. 2016

Journal of Applied Physics

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Materials undergoing antiferroelectric/ferroelectric (AFE/FE) transitions are studied for possible applications that exploit the large volume, charge and entropy differences between the two states, such as electrocaloric cooling, energy storage, electromechanical actuators. Though certain compositions of PbZr1−xTixO3 (PZT) codoped with La and Sn may withstand millions of electrically induced AFE/FE cycles, in other cases few thermally induced cycles and room temperature aging may cause noticeable changes in the material properties. This is particularly evident in the elastic moduli, which at room temperature can become as much as four times softer. In order to get more insight into the mechanisms involved in such elastic aging and full recovering with mild annealing at 600 − 800 K, the effect of La doping on PbZr0.954Ti0.046O3 is studied with anelastic measurements. Complete suppression of the time dependent phenomena is found after the transformation of the intermediate FE phase into incommensurate AFE by 2% La doping. This is discussed in terms of disappearance of the stress and electric fields at the FE/AFE interfaces, in the light of the thermally activated anelastic relaxation processes that are observed at high temperature, and are due to mobile defects, presumably O vacancies.

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Piezoelectric softening in ferroelectrics: Ferroelectric versus antiferroelectricPbZr1−xTixO3

Cited by 21 publications

References 26 publications

Probing ferroelectricity in highly conducting materials through their elastic response: Persistence of ferroelectricity in metallic BaTiO3−δ

Probing ferroelectricity in highly conducting materials through their elastic response: Persistence of ferroelectricity in metallic BaTiO3−δ

Ionic Mobility and Phase Transitions in Perovskite Oxides for Energy Application

Elastic aging from coexistence and transformations of ferroelectric and antiferroelectric states in PZT

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