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Author: search.filters.author.T-Thienprasert, JirarojSubject: search.filters.subject.First-principles calculations

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    First-principles study of Bi and Al in orthorhombic PbZrO3
    (2016-04-01)
    Chotsawat, Maneerat
    ;
    Sarasamak, Kanoknan
    ;
    Thanomngam, Pitiporn
    ;
    Limpijumnong, Sukit
    ;
    T-Thienprasert, Jiraroj
    Lead zirconate PbZrO<inf>3</inf> (PZO) is one of the most important ceramic materials due to its antiferroelectric property, which can be used in many technological applications. Due to the toxicity of Pb, there is an attempt to replace Pb with other non-toxic elements. It has been reported that doping orthorhombic-PZO with Bi and Al atoms could stabilize the antiferroelectric property in a wide temperature range and reduce the lead content in the material. In this work, we used first-principles calculations based on density functional theory to investigate the microscopic and electronic structures of Bi and Al defects in orthorhombic-PZO. Our calculated defect formation energies revealed that Bi atom can substitute on either Pb site (A-site) or Zr site (B-site); depending on the Fermi-level as well as the crystal growth condition. On the other hand, Al atom is likely to substitute only on the Zr site. In addition, our calculations revealed that there is only a small binding between Bi<inf>Pb</inf> and adjacent Al<inf>Zr</inf> or Bi<inf>Zr</inf> with the binding energies of ∼0.2 eV. This indicates that Bi<inf>Pb</inf> and Al<inf>Zr</inf> (or Bi<inf>Zr</inf>) are unlikely to form complexes.
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    X-ray absorption spectroscopy of indium nitride, indium oxide, and their alloys
    (2010-04-16)
    T-Thienprasert, Jiraroj
    ;
    Rujirawat, Saroj
    ;
    Nukeaw, Jiti
    ;
    Limpijumnong, Sukit
    To investigate the local structure of InN, In<inf>2</inf>O<inf>3</inf> and their alloys, synchrotron (In L<inf>3</inf>-edge) X-ray absorption near edge structures (XANES) of indium oxynitride samples with varied O contents are used in conjunction with first-principles calculations. A good agreement between the measured and simulated spectra is obtained. It is found that the spectra are sensitive to the coordination number of the In atoms, i.e., fourfold for InN-like structures and sixfold for In<inf>2</inf>O<inf>3</inf>-like structures. Moreover, the spectra are quite insensitive to the species (N or O) around In. The calculated band structures and density of states are also presented and discussed. © 2010 Elsevier B.V. All rights reserved.