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Hafnium-Silicon Precipitate Structure Determination in a New Heat-Resistant Ferritic Alloy by Precession Electron Diffraction Techniques

Published online by Cambridge University Press:  30 October 2013

Désirée Viladot ,
Joaquim Portillo ,
Mauro Gemí ,
Stavros Nicolopoulos  and
Núria Llorca-Isern
Désirée Viladot
Affiliation:
Departament de Ciència de Materials i Enginyeria Metal·lúrgica, Facultat de Química, Universitat de Barcelona, C/Martí i Franquès 1-11, Barcelona 08028, Spain
Joaquim Portillo
Affiliation:
Centres Cientifics i Tecnològics (CCiT), Universitat de Barcelona/Solé i Sabaris 1-3, Barcelona 08028, Spain NanoMEGAS, Boulevard Edmond Machtens 79, Brussels B-1080, Belgium
Mauro Gemí
Affiliation:
Center for Nanotechnology Innovation@NEST, Istituto Italiano di Tecnologia, Pisa 56127, Italy
Stavros Nicolopoulos
Affiliation:
NanoMEGAS, Boulevard Edmond Machtens 79, Brussels B-1080, Belgium
Núria Llorca-Isern*
Affiliation:
Departament de Ciència de Materials i Enginyeria Metal·lúrgica, Facultat de Química, Universitat de Barcelona, C/Martí i Franquès 1-11, Barcelona 08028, Spain
*
*Corresponding author. E-mail: [email protected]
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Abstract

The structure determination of an HfSi4 precipitate has been carried out by a combination of two precession electron diffraction techniques: high precession angle, 2.2°, single pattern collection at eight different zone axes and low precession angle, 0.5°, serial collection of patterns obtained by increasing tilts of 1°. A three-dimensional reconstruction of the associated reciprocal space shows an orthorhombic unit cell with parameters a = 11.4 Å, b = 11.8 Å, c = 14.6 Å, and an extinction condition of (hkl) h + k odd. The merged intensities from the high angle precession patterns have been symmetry tested for possible space groups (SG) fulfilling this condition and a best symmetrization residual found at 18% for SG 65 Cmmm. Use of the SIR2011 direct methods program allowed solving the structure with a structure residual of 18%. The precipitate objects of this study were reproducibly found in a newly implemented alloy, designed according to molecular orbital theory.

Keywords

precession electron diffractionprecession-assisted tomographic diffractioncrystal structure determinationhafnium–silicon precipitate
Type
Materials Applications
Information
Microscopy and Microanalysis , Volume 20 , Issue 1 , February 2014 , pp. 25 - 32
Copyright
Copyright © Microscopy Society of America 2014 

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