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Subject: search.filters.subject.D. Perovskite

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    Sound velocities and elastic properties of PbTiO3 and PbZrO 3 under pressure: First principles study
    (2013-05-01)
    Pandech, Narasak
    ;
    Sarasamak, Kanoknan
    ;
    Limpijumnong, Sukit
    The elastic constants and sound velocities as a function of pressure for perovskite materials PbTiO<inf>3</inf> (PTO) and PbZrO<inf>3</inf> (PZO) were investigated by first principles calculations. Under ambient pressure, the calculated structural parameters were calculated and found to be in good agreement with known values. To study properties under pressure, PTO and PZO were calculated at several reduced volumes, each of which corresponds to the system under pressure. The C<inf>11</inf>, C<inf>12</inf> and C<inf>44</inf> elastic constants are all found to increase with pressure for the pressure range studied. Because the sound velocities are directly derived from the elastic constants, the relationships between the sound velocities and pressure also follow similar trends. The longitudinal modes are all larger than those of the transverse modes. © 2012 Elsevier Ltd and Techna Group S.r.l.
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    Crystal structure, microstructure and electrical properties of (1-x-y)Bi0.5Na0.5TiO3-xBi0.5K 0.5TiO3-yBiFeO3 ceramics near MPB prepared via the combustion technique
    (2013-05-01)
    Sumang, Rattiphorn
    ;
    Vittayakorn, Naratip
    ;
    Bongkarn, Theerachai
    (1-x-y)Bi<inf>0.5</inf>Na<inf>0.5</inf>TiO<inf>3</inf>-xBi <inf>0.5</inf>K<inf>0.5</inf>TiO<inf>3</inf>-yBiFeO<inf>3</inf> (BNKFT-x/y with 0.12≤x≤0.24, 0≤y≤0.07) lead-free piezoelectric ceramics have been prepared by the combustion technique. The effects of amounts of x and y on structures and electrical properties were examined. Powders and ceramics can be well calcined and sintered at 750 °C for 2 h and 1025-1050 °C, respectively. The results indicated that the crystalline structure and microstructure changed with the increase of x and y concentrations. XRD results of BNKFT-x/0.03 and BNKFT-0.18/y ceramics with 0.12≤x≤0.24 and 0≤y≤0.07 showed the rhombohedral-tetragonal morphotropic phase boundary (MPB). The addition of y caused a promoted grain growth while the addition of x suppressed the grain growth. The highest density (ρ=5.85 g/cm<sup>3</sup>), superior dielectric properties at T<inf>c</inf> (ε<inf>r</inf>=7846 and tan δ=0.02), remnant polarization measured at 40 kV/cm (P<inf>r</inf> = 20.1 μC/cm<sup>2</sup>) and piezoelectric coefficient (d<inf>33</inf>=213 pC/N) were obtained for x=0.18 and y=0.03. © 2012 Elsevier Ltd and Techna Group S.r.l.