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Author: search.filters.author.Rujijanagul, GobwuteSubject: search.filters.subject.Dielectric properties

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    The effect of post-sintering annealing induced extrinsic dielectric properties in PZT-PZN ceramics
    (2007-08-02)
    Vittayakorn, Naratip
    ;
    Cann, David P.
    ;
    Rujijanagul, Gobwute
    ;
    Tunkasiri, Tawee
    Pb[(Zr1/2Ti1/2)0.7(Zn1/3Nb2/3)0.3]O3 (PZT-30PZN) powder was prepared using the columbite precursor method. The phase development of calcined powder precursors was analyzed by X-ray diffraction. Dielectric and ferroelectric properties of the as-sintered and annealed samples were measured and correlated with microstructure. The morphology evolution was determined by a scanning electron microscopy (SEM) technique. The as-sintered ceramic exhibited weak relaxor-ferroelectric behavior, with a relatively low dielectric constant maximum measured at 1 kHz (Km@1 kHz) of 14 000. Annealing resulted in a transition to normal-ferroelectric-like behavior, a shift in the dielectric maximum temperature from 310C to 300C, and a dramatic increase of Km@1 kHz to a maximum value of 25 100 for the longer anneal. After thermal annealing at 900C for 1 week a strong enhancement of remanent polarization (Pr) was observed.
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    The improvement in dielectric and ferroelectric performance of PZT-PZN ceramics by thermal treatment
    (2007-07-01)
    Vittayakorn, Naratip
    ;
    Rujijanagul, Gobwute
    ;
    Cann, David P.
    Pyrochlore-free lead zirconate titanate - lead zinc niobate ceramics have been systematically investigated in the as-sintered condition as well as after annealing. The ceramics were characterized by dielectric spectroscopy and Sawyer-Tower polarization (P-E) measurements. The powders of Pb[(Zr<inf>1/2</inf>Ti<inf>1/2</inf>)<inf>(1-x)</inf>-(Zn<inf>1/3</inf>Nb<inf>2/3</inf>)<inf>x</inf>]O<inf>3</inf>, where x = 0.1, 0.3 and 0.5 were prepared using the columbite-(wolframite) precursor method. The general trend seems to indicate that the annealed samples become more normal-ferroelectric-like behavior as opposed to the relaxor-ferroelectric-like behavior observed in the as-sintered state. The as-sintered 0.9PZT-0.1PZN ceramic exhibited weak relaxor-ferroelectric behavior, with a relatively low dielectric constant maximum of 14,000 measured at 1 kHz. Annealing resulted in a transition to normal-ferroelectric-like behavior, a shift in the dielectric maximum temperature from 360 °C to 350 °C, and a dramatic increase in the dielectric constant at 1 kHz to a maximum value of 35,000 for the longer anneal. After thermal annealing at 900 °C for one week a strong enhancement of remanent polarization (P<inf>r</inf>) was observed. © 2007 Elsevier B.V. All rights reserved.
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    Phase transition, mechanical, dielectric and piezoelectric properties of perovskite (Pb1-xBax)ZrO3 ceramics
    (2007-01-01)
    Vittayakorn, Naratip
    ;
    Bongkarn, Theerachai
    ;
    Rujijanagul, Gobwute
    (Pb<inf>1-x</inf>Ba<inf>x</inf>)ZrO<inf>3</inf> ceramics were prepared in the composition range 0.00≤x≤0.30 by the mixed oxide solid-state reaction method. The samples were kept at the calcination temperature 1000 °C for 1 h and at the sintering temperature 1300 °C for 3 h. The structural phase transitions and the dielectric properties were studied. It was found that the density of the ceramics decreases with increasing amount of Ba<sup>2+</sup>, whilst the average grain size is in the range 1-2.3 μm. The structure of as-calcined powder reveals that the fraction of the orthorhombic phase is decreasing with increasing Ba<sup>2+</sup> content. The values of Vickers and Knoop hardness are in the range of 4.10-6.48 and 4.15-5.67 GPa, respectively. Dielectric measurements show that the antiferroelectric phase (AFE)-ferroelectric phase (FE) and the FE to paraelectric phase (PE) phase transformation temperatures decrease with increasing Ba<sup>2+</sup> concentration. The AFE-FE phase transformation is detected for compositions 0.00≤x≤0.075. The maximum dielectric constant gradually increases with increasing composition up to x=0.20. For higher Ba<sup>2+</sup> concentrations, the lowering of the maximum dielectric value is accompanied by a progressive broadening of the permittivity peak. The d<inf>33</inf> values of the samples increase from ∼0 to 87 pC/N with increasing Ba<sup>2+</sup> concentration from x=0.00 to 0.30. © 2006 Elsevier B.V. All rights reserved.