Investigation of a relationship between dielectric peak diffuseness and elastic modulus variations in a ferroelectric relaxor

L. G. Sarasúa; A. Moreno; S. Favre; J. A. Eiras

doi:10.1063/1.4869200

Investigation of a relationship between dielectric peak diffuseness and elastic modulus variations in a ferroelectric relaxor

Journal of Applied Physics ◽

10.1063/1.4869200 ◽

2014 ◽

Vol 115 (11) ◽

pp. 114110

Author(s):

L. G. Sarasúa ◽

A. Moreno ◽

S. Favre ◽

J. A. Eiras

Keyword(s):

Elastic Modulus ◽

Ferroelectric Relaxor ◽

Dielectric Peak

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Structure and Dielectric Behavior of Yb2O3-MgO Co-Doped 0.92BaTiO3-0.08(Na0.5Bi0.5)TiO3 Ferroelectric Relaxor

Materials ◽

10.3390/ma14226802 ◽

2021 ◽

Vol 14 (22) ◽

pp. 6802

Author(s):

Xiao-Hu Ren ◽

Dong-Yun Gui

Keyword(s):

Variable Temperature ◽

Dielectric Behavior ◽

Phase Changes ◽

Core Shell ◽

Shell Microstructure ◽

Temperature Dependent ◽

Raman Analysis ◽

Ferroelectric Relaxor ◽

Dielectric Peak ◽

Xrd And Tem

Dielectric properties and structure of 0.015Yb2O3-xMgO doped 0.92BaTiO3-0.08(Na0.5Bi0.5)TiO3 ceramics with x = 0.0–0.025 have been investigated. As Yb2O3-MgO was added into the BT-NBT, the phase changes from tetragonal to pseudo-cubic, with the tetragonality c/a decreases from 1.011 to 1.008 and XRD peaks broadened. The combined study of XRD and TEM image revealed a formation of core–shell structure in grains with core of 400–600 nm and the shell of a thickness 60–200 nm. There is a slowly phase transition against temperature from the variable temperature Raman analysis. The ferroelectric relaxor peak of BT-NBT decreases from ~4000 to ~2000 and a new broad dielectric peak with an equivalent maximum (εr′~2300) appears in the temperature dependent dielectric constant curve (εr′-T), which produces a flat εr′-T curve. Sample 0.92BaTiO3-0.08(Na0.5Bi0.5)TiO3-0.015Yb2O3-0.005 MgO and 0.92BaTiO3-0.08(Na0.5Bi0.5)TiO3-0.015Yb2O3-0.01MgO give a εr′ variation within ±14% and ±10% in 20–165 °C. The core–shell microstructure should take account for the flattened εr′–T behavior of these samples.

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Effect Of Elevated Temperatures On Complete Concrete Deformation Diagrams

Promyshlennoe i Grazhdanskoe Stroitel stvo ◽

10.33622/0869-7019.2019.11.09-14 ◽

2019 ◽

pp. 9-14

Keyword(s):

Experimental Data ◽

Elastic Modulus ◽

Elevated Temperatures ◽

Peak Load ◽

Relative Deformation ◽

Deformation Characteristics ◽

Compression Tests ◽

Strain Behavior ◽

Different Temperatures ◽

Deformation Diagrams

The analysis of the previous results of the study on concrete stress-strain behavior at elevated temperatures has been carried out. Based on the analysis, the main reasons for strength retrogression and elastic modulus reduction of concrete have been identified. Despite a significant amount of research in this area, there is a large spread in experimental data received, both as a result of compression and tension. In addition, the deformation characteristics of concrete are insufficiently studied: the coefficient of transverse deformation, the limiting relative compression deformation corresponding to the peak load and the almost complete absence of studies of complete deformation diagrams at elevated temperatures. The two testing chambers provided creating the necessary temperature conditions for conducting studies under bending compression and tension have been developed. On the basis of the obtained experimental data of physical and mechanical characteristics of concrete at different temperatures under conditions of axial compression and tensile bending, conclusions about the nature of changes in strength and deformation characteristics have been drawn. Compression tests conducted following the method of concrete deformation complete curves provided obtaining diagrams not only at normal temperature, but also at elevated temperature. Based on the experimental results, dependences of changes in prism strength and elastic modulus as well as an equation for determining the relative deformation and stresses at elevated temperatures at all stages of concrete deterioration have been suggested.

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