scholarly journals Energy-filtered electron diffuse scattering of ferroelectrics PMN and PMN-xPT

2014 ◽  
Vol 70 (a1) ◽  
pp. C623-C623
Author(s):  
Jerome Pacaud ◽  
Wajdi Saidi ◽  
Ray Withers ◽  
Brahim Dkhil ◽  
Jian-Min Zuo
Keyword(s):  
Diffuse Scattering ◽  
Phonon Scattering ◽  
Relaxor Ferroelectrics ◽  
Charge Ordering ◽  
Diffuse Intensity ◽  
Sufficient Energy ◽  
Direct Lattice ◽  
Imaging Plates ◽  
Dielectric And Piezoelectric Properties

PbMb1/3Nb2/3O3 (PMN) and its solid solution (1-x)PbMb1/3Nb2/3O3-(x)PbTiO3 (PMN-xPT) are relaxor ferroelectrics which have attracted attention in the last few decades because of their very interesting dielectric and piezoelectric properties and have since be two of the most extensively studied. All the previous studies emphasized the role of the local structural fluctuations leading to local changes in symmetries [1] due to displacements of ions in the unit-cell. We studied PMN and PMN-xPT by electron diffuse scattering using an in-column energy filter and Imaging-Plates as detector. We found evidences for streaks of intensity along the [110]* direction as previously found in PbZn1/3Nb2/3O3 (PZN) with neutron diffraction [2]. Moreover, weak diffuse scattering sheets can be observed along (111)* reciprocal planes showing the existence of correlations along the [111] directions of the direct lattice. Figure 1 shows a diffraction pattern taken along [02-1] zone axis presenting both diffuse features. This can be related to the displacement of Pb ions along the diagonals of the cube found by simulation [3] but greatly complexify the analysis of the shape of the diffuse intensity. Compared to the neutron, electron diffraction has the advantage of two dimensional recording of diffuse scattering and eventually sensitivity to charge ordering but quantitative analysis is limited due to the complication of multiple scattering and the lack of sufficient energy resolution for the study of inelastic phonon scattering.

Lattice Thermal Conductivity Modelling of a Diatomic Nanoscale Material

2020 ◽  
Vol 10 (5) ◽  
pp. 602-609
Author(s):  
Adil H. Awad
Keyword(s):  
Thermal Conductivity ◽  
Lattice Thermal Conductivity ◽  
Phonon Scattering ◽  
Correction Term ◽  
Nanoscale Material ◽  
New Approach ◽  
Two Samples ◽  
Conductivity Modelling ◽  
Callaway Model

Introduction: A new approach for expressing the lattice thermal conductivity of diatomic nanoscale materials is developed. Methods: The lattice thermal conductivity of two samples of GaAs nanobeam at 4-100K is calculated on the basis of monatomic dispersion relation. Phonons are scattered by nanobeam boundaries, point defects and other phonons via normal and Umklapp processes. Methods: A comparative study of the results of the present analysis and those obtained using Callaway formula is performed. We clearly demonstrate the importance of the utilised scattering mechanisms in lattice thermal conductivity by addressing the separate role of the phonon scattering relaxation rate. The formulas derived from the correction term are also presented, and their difference from Callaway model is evident. Furthermore their percentage contribution is sufficiently small to be neglected in calculating lattice thermal conductivity. Conclusion: Our model is successfully used to correlate the predicted lattice thermal conductivity with that of the experimental observation.

Relative Contributions of Inelastic and Elastic Diffuse Phonon Scattering to Thermal Boundary Conductance Across Solid Interfaces

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Patrick E. Hopkins ◽  
Pamela M. Norris
Keyword(s):  
Experimental Data ◽  
Elastic Scattering ◽  
Inelastic Scattering ◽  
Debye Temperature ◽  
Diffuse Scattering ◽  
Phonon Scattering ◽  
Interfacial Transport ◽  
Thermal Boundary Conductance ◽  
Dielectric Interfaces ◽  
Scattering Events

The accuracy of predictions of phonon thermal boundary conductance using traditional models such as the diffuse mismatch model (DMM) varies depending on the types of material comprising the interface. The DMM assumes that phonons, undergoing diffuse scattering events, are elastically scattered, which drives the energy conductance across the interface. It has been shown that at relatively high temperatures (i.e., above the Debye temperature) previously ignored inelastic scattering events can contribute substantially to interfacial transport. In this case, the predictions from the DMM become highly inaccurate. In this paper, the effects of inelastic scattering on thermal boundary conductance at metal/dielectric interfaces are studied. Experimental transient thermoreflectance data showing inelastic trends are reviewed and compared to traditional models. Using the physical assumptions in the traditional models and experimental data, the relative contributions of inelastic and elastic scattering to thermal boundary conductance are inferred.

Experimental measurement of electron diffuse scattering in magnetite using energy-filter and imaging plates

Micron ◽  
2000 ◽  
Vol 31 (5) ◽  
pp. 527-532 ◽  
Author(s):  
J.M. Zuo ◽  
J. Pacaud ◽  
R. Hoier ◽  
J.C.H. Spence
Keyword(s):  
Experimental Measurement ◽  
Diffuse Scattering ◽  
Imaging Plates

Analysis of diffuse scattering from the mineral mullite

1994 ◽  
Vol 27 (5) ◽  
pp. 742-754 ◽  
Author(s):  
B. D. Butler ◽  
T. R. Welberry
Keyword(s):  
Diffuse Scattering ◽  
Real Space ◽  
Order Parameters ◽  
Scattering Data ◽  
Local Order ◽  
Near Neighbour ◽  
Diffuse Intensity ◽  
Space Model ◽  
Least Squares Techniques ◽  
Space Volume

A full reciprocal-space volume of diffuse scattering data from a single-crystal of the mineral mullite, Al2(Al2 + 2x Si2 − 2x )O10 − x , x = 0.4, was collected. These data were analysed using least-squares techniques by writing an equation for the diffuse scattering that involves only the local order between vacancies on specific oxygen sites in the material. The effect of the large, but predictable, cation shifts on the diffuse intensity is taken account of in the coefficients of the oxygen-vacancy short-range-order intensities. This analysis shows that the vacancies are negatively correlated at the near-neighbour ½ 〈110〉, [110], 〈001〉 and 〈011〉 interatomic vectors and positively correlated along the 〈010〉, 〈101〉, ½ 〈112〉 and ½ 〈310〉 vectors. Subsequent Monte Carlo modelling of the structure based on these local-order parameters demonstrates that the structure of mullite is dominated by effective near-neighbour vacancy–vacancy repulsive interactions. A real-space model of mullite is presented that is approximately consistent with the measured local-order parameters.

Role of electronic correlation effect on charge ordering in β-V2OPO4

2020 ◽  
Vol 173 ◽  
pp. 109433
Author(s):  
Runxue Wang ◽  
Xipeng Zhang ◽  
Hengyang Xie ◽  
Yuanhui Xu ◽  
Keju Sun ◽  
...  
Keyword(s):  
Correlation Effect ◽  
Charge Ordering ◽  
Electronic Correlation

NEUTRON DIFFUSE SCATTERING IN LEAD-BASED RELAXOR FERROELECTRICS AND ITS RELATIONSHIP TO THE ULTRA-HIGH PIEZOELECTRICITY

2012 ◽  
Vol 02 (02) ◽  
pp. 1241005 ◽  
Author(s):  
PETER M. GEHRING
Keyword(s):  
Dielectric Properties ◽  
Single Crystal ◽  
Phase Boundary ◽  
Morphotropic Phase Boundary ◽  
Diffuse Scattering ◽  
Short Range ◽  
Piezoelectric Coefficient ◽  
Relaxor Ferroelectrics ◽  
Scattering Measurements

A brief review is presented that summarizes recent neutron diffuse scattering measurements on single crystal PbMg1/3Nb2/3O3 (PMN) and PbZn1/3Nb2/3O3 (PZN) doped with PbTiO3 (PT). Emphasis is placed on results that suggest that the short-range, polar correlations observed in these systems are connected to the anomalous relaxor dielectric properties, and in particular to the large values of the piezoelectric coefficient d33 near the morphotropic phase boundary.

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