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Author: search.filters.author.Bhupaijit, PamornnarumolSubject: search.filters.subject.ferroelectric

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    Effect of Co2+ substitution in B-sites of the perovskite system on the phase formation, microstructure, electrical and magnetic properties of Bi0.5(Na0.68K0.22Li0.10)0.5TiO3 ceramics
    (2022-09-01)
    Bhupaijit, Pamornnarumol
    ;
    Kaewsai, Chonnarong
    ;
    Suriwong, Tawat
    ;
    Pinitsoontorn, Supree
    ;
    Yotthuan, Surirat
    Bi<inf>0.5</inf>(Na<inf>0.68</inf>K<inf>0.22</inf>Li<inf>0.10</inf>)<inf>0.5</inf>Ti<inf>1−x</inf>Co<inf>x</inf>O<inf>3</inf> lead-free perovskite ceramics (BNKLT−xCo, x = 0, 0.005, 0.010, 0.015 and 0.020) were fabricated via the solid-state combustion technique. A small-amount of Co<sup>2+</sup> ion substitution into Ti-sites led to modification of the phase formation, microstructure, electrical and magnetic properties of BNKLT ceramics. Coexisting rhombohedral and tetragonal phases were observed in all samples using the X-ray diffraction (XRD) technique. The Rietveld refinement revealed that the rhombohedral phase increased from 39% to 88% when x increased from 0 to 0.020. The average grain size increased when x increased. With increasing x, more oxygen vacancies were generated, leading to asymmetry in the bipolar strain (S−E) hysteresis loops. For the composition of x = 0.010, a high dielectric constant (ε<inf>m</inf>) of 5384 and a large strain (S<inf>max</inf>) of 0.23% with the normalized strain (d*<inf>33</inf>) of 460 pm·V<sup>−1</sup> were achieved. The BNKLT−0Co ceramic showed diamagnetic behavior but all of the BNKLT−xCo ceramics exhibited paramagnetic behavior, measured at 50 K.
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    Firing Temperature Effects on Phase Formation, Microstructure and Electrical Properties of BNKLT-Sm Ceramics
    (2022-01-01)
    Klinbanmor, Metarsit
    ;
    Bhupaijit, Pamornnarumol
    ;
    Charoonsuk, Thitirat
    ;
    Wanakamol, Panitan
    ;
    Vittayakorn, Naratip
    Lead-free Bi<inf>0.5</inf>(Na<inf>0.68</inf>K<inf>0.22</inf>Li<inf>0.10</inf>)<inf>0.5</inf>TiO<inf>3</inf> + 0.003 mol Sm<inf>2</inf>O<inf>3</inf> (BNKLT-Sm) ceramics were synthesized via the solid-state combustion technique with calcination temperatures between 750 and 850 °C and sintering temperatures between 1025 and 1100 °C for 2 h. The results showed that increasing the calcination temperature caused the percentage of perovskite phase and the particle size of the BNKLT-Sm powders increased. The BNKLT-Sm powder calcined at 800 °C displayed a pure perovskite structure without any impurity phases. The influence of the sintering temperature on the phase formation, microstructure and electrical properties of the ceramics was then investigated. All samples sintered at different temperatures possessed coexisting rhombohedral (R) and tetragonal (T) phases and the R phase became dominant when the sintering temperature increased. The microstructure of all ceramics showed a rectangular shape and anisotropic growth. The average grain size increased with increasing sintering temperature. Dielectric and ferroelectric behavior displayed relaxor characteristics in all samples. The maximum dielectric constant at T<inf>m</inf> (ε<inf>m</inf>) of 4777 and the highest remnant polarization (P<inf>r</inf>) of 5.03 µC/cm<sup>2</sup> were obtained by the densest ceramics (5.85 g/cm<sup>3</sup>), which was sintered at 1075 °C for 2 h.
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    Effect of substitution of (NiNb)4+ into B-sites on the phase formation, microstructure and electrical properties of Bi0.47Na0.47Ba0.06TiO3 ceramics
    (2022-01-01)
    Luangpangai, Anupong
    ;
    Bhupaijit, Pamornnarumol
    ;
    Charoenthai, Nipaphat
    ;
    Vittayakorn, Naratip
    ;
    Thountom, Sarawut
    Bi<inf>0.47</inf>Na<inf>0.47</inf>Ba<inf>0.06</inf>Ti<inf>1-x</inf>(Ni<inf>1/3</inf>Nb<inf>2/3</inf>)<inf>x</inf>O<inf>3</inf> ceramics (abbreviated as BNBT<inf>1-x</inf>(NN)<inf>x</inf>, x = 0, 0.01, 0.03 and 0.05) were synthesized by solid-state combustion. The effect of x on the phase formation, microstructure and electrical properties of BNBT<inf>1-x</inf>(NN)<inf>x</inf> ceramics was examined. The XRD pattern indicated the coexistence of rhombohedral and tetragonal phases in all the specimens. Moreover, Rietveld refinement confirmed that the tetragonal phase increased from 47 to 71% when x increased from 0 to 0.05. The morphology of BNBT<inf>1-x</inf>(NN)<inf>x</inf> ceramics was observed by SEM and the ceramics grains showed polygonal shapes and the grain growth tended to be anisotropic. With (NiNb)<sup>4+</sup> substitution, the average grain sized decreased rapidly from 1.7 to 1.0 µm and the grain size distribution was narrower as the amount of (NiNb)<sup>4+</sup> increased. The density, remnant polarization (P<inf>r</inf>) and coercive field (E<inf>c</inf>) rapidly decreased with increasing x. A significant decrease in the ferroelectric properties was caused by the increasing tetragonal phase.