arXiv subjects

Mohamed Gouné

Publications and source records attributed to Mohamed Gouné.

3 recordsLinked to original sources

arXiv2019

Reflections on the analysis of interfaces and grain boundaries by atom probe tomography

Interfaces play critical roles in materials, and are usually both structurally and compositionally complex microstructural features. The precise characterization of their nature in three-dimensions at the atomic-scale is one of the grand challenges for microscopy and microanalysis, as this information is crucial to establish structure-property relationships. Atom probe tomography is well-suited to analyzing the chemistry of interfaces at the nanoscale. However, optimizing such microanalysis of interfaces requires great care in the implementation across all aspects of the technique, from specimen preparation to data analysis and ultimately the interpretation this information. This article provides critical perspectives on key aspects pertaining to spatial resolution limits and the issues with compositional analysis that can limit the quantification of interface measurements. Here, we use the example of grain boundaries in steels, however the results are applicable for the characterization of grain boundaries and transformation interfaces in a very wide range of industrially relevant engineering materials.

cond-mat.mtrl-sci↗

arXiv2018

Enhancement of dielectric properties of lead-free BCZT ferroelectric ceramics by grain size engineering

Lead-free Ba0.85Ca0.15Ti0.9Zr0.1O3 (BCZT) ceramics had attracted much attention for the fabrication of microelectronic devices by virtue of their excellent dielectric, ferroelectric and piezoelectric properties. To understand the effects of both mean grain size and grain size distribution on the dielectric properties of lead-free Ba0.85Ca0.15Ti0.9Zr0.1O3 (BCZT) ferroelectric relaxors, an original method was proposed. It is based on the surfactant-assisted solvothermal processing coupled with low-temperature conventional sintering at 1250 °C. In this way, three highly dense BCZT with different mean grain size and dissimilar grain size distribution were designed. A significant increase of dielectric properties was obtained by a control of grain size and densification process. The dielectric constants measured were ranged from 5370 to 9646 and the dielectric loss was enhanced by 70%. Surprisingly, it was evidenced that there is unequivocal link between mean grain size with dielectric properties. Indeed, it was found that the presence of high density of refined grains leads to an improvement of dielectric properties due to an enhancement of densification. This work may provide a new strategy to design ferroelectric materials with enhanced properties.

physics.app-ph↗

arXiv2018

Very-low temperature synthesis of pure and crystalline lead-free Ba0.85Ca0.15Zr0.1Ti0.9O3 ceramic

The site-doping strategy of barium titanate (BaTiO3) is a promising way to develop new lead-free materials for energy with enhanced dielectric and piezoelectric properties. A novel strategy to elaborated pure and crystalline Ba0.85Ca0.15Zr0.1Ti0.9O3(BCZT) ferroelectric powders at low temperature is proposed. It is based on sol-gel method followed by a hydrothermal reaction. The effects of preparation temperature on structure, crystallinity, purity, morphology and particles size distribution of BCZT powders were studied. It was clearly shown that pure and crystalline BCZT could be obtained over 80°C. Furthermore, the BCZT particles exhibit a spherical shape whose mean size increases from 145 nm at 40°C to 160 nm at 80°C. The present study may provide a new strategy to design lead-free ferroelectric materials with enhanced structure and microstructure properties at very low temperature.

cond-mat.mtrl-sci↗