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Author: search.filters.author.Rujijanagul, GobwuteSubject: search.filters.subject.Phase transitions

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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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    Investigation of the influence of thermal treatment on the morphologies, dielectric and ferroelectric properties of PZT-based ceramics
    (2007-08-16)
    Vittayakorn, Naratip
    ;
    Rujijanagul, Gobwute
    ;
    Cann, David P.
    Pb[(Zr<inf>1/2</inf>Ti<inf>1/2</inf>)<inf>0.9</inf>(Zn<inf>1/3</inf>Nb<inf>2/3</inf>)<inf>0.1</inf>]O<inf>3</inf> (PZT-10PZN) 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 the microstructure. The morphological evolution was determined by scanning electron microscopy (SEM). The as-sintered ceramic exhibited weak normal-ferroelectric behavior, with a relatively low dielectric constant maximum measured at 1 kHz (ε<inf>rmax</inf> at 1 kHz) of 13,000. Annealing resulted in a transition to relaxor-ferroelectric-like behavior, a shift in the dielectric maximum temperature from 360 to 350 °C, and a dramatic increase in ε<inf>rmax</inf> at 1 kHz to a maximum value of 35,000 for the longer anneal. Furthermore, after thermal annealing at 900 °C for 1 week the composition shifted close to the MPB with a great reduction in the transition temperature and a broadening of the dielectric constant maximum. A strong enhancement of the remanent polarization (P<inf>r</inf>) was also observed. © 2006 Elsevier B.V. All rights reserved.