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Author: search.filters.author.Thatawong, BhoowadolSubject: search.filters.subject.dielectric

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    Phase Formation, Morphology and Electrical Properties of Lead-Free BNBLT-xBSN Ceramics Synthesized via the Solid-State Combustion Technique
    (2023-01-01)
    Thatawong, Bhoowadol
    ;
    Vittayakorn, Naratip
    ;
    Rittidech, Aurawan
    ;
    Bongkarn, Theerachai
    Lead-free 1-x(Bi<inf>0.47</inf>Na<inf>0.47</inf>Ba<inf>0.06</inf>)<inf>0.95</inf>La<inf>0.05</inf>TiO<inf>3</inf>-xBa(Sn<inf>0.70</inf>Nb<inf>0.24</inf>)O<inf>3</inf> (BNBLT-xBSN) ceramics with x = 0, 0.01, 0.02, 0.03 and 0.04 mol.% were synthesized by the solid-state combustion technique with a calcination temperature of 750 °C for 2 h and a sintering temperature of 1150 °C for 2 h. The effect of BSN substitution on the phase formation, microstructure, dielectric, ferroelectric and energy storage properties of the BNBLT ceramics was investigated. With the substitution of BSN, the coexisting rhombohedral (R) and tetragonal (T) phases transformed into coexisting R and cubic (C) phase, verified by Rietveld refinement. The C phase increased with increased BSN content. The average grain size decreased from 1.14 to 0.89 µm when x increased to 0.03 and then increased to 0.96 µm. The measured density and maximum dielectric constant (ε <inf>m</inf>) tended to increase from 5.44 to 5.87 g/cm<sup>3</sup> and 1800 to 1942 when x increased to 0.03, then decreased to 5.25 g/cm<sup>3</sup> and 1501, respectively. The remanent polarization (P <inf>r</inf>) and coercive field (E <inf>c</inf>) decreased when x increased to 0.03. The 0.97BNBLT-0.03BSN ceramic exhibited the lowest energy loss density (W <inf>loss</inf> ∼ 0.10 J/cm<sup>3</sup>) and the highest energy-storage efficiency (η ∼ 77.3%) measured under an electric field of 70 kV/cm.
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    Phase Structure, Microstructure, and Electrical Properties of Bi0.47Na0.47Ba0.06TiO3 Ceramics with (LiNb)4+ Substituted into B-Sites
    (2023-01-01)
    Luangpangai, Anupong
    ;
    Thatawong, Bhoowadol
    ;
    Charoenthai, Nipaphat
    ;
    Vittayakorn, Naratip
    ;
    Bongkarn, Theerachai
    Due to the substitution of complex ions into B-sites is very interesting in recent, lead-free Bi<inf>0.47</inf>Na<inf>0.47</inf>Ba<inf>0.06</inf>Ti<inf>1−</inf><inf>x</inf> (LiNb) <inf>x</inf> O<inf>3</inf> (BNBT<inf>1−</inf><inf>x</inf> LN <inf>x</inf>) ceramics (with x = 0–0.04) were fabricated by the solid-state combustion method. The influence of (LiNb)<sup>4+</sup> (x) on the phase structure, microstructure, and electrical properties was investigated. The X-ray diffraction (XRD) patterns exhibited a pure perovskite structure for all specimens. Coexisting rhombohedral and tetragonal phases were observed in all samples and the tetragonal phase increased with increased x, as analyzed by the Rietveld refinement method. The morphology of the BNBT<inf>1−</inf><inf>x</inf> LN <inf>x</inf> ceramics, obtained by scanning electron microscopy (SEM), revealed almost-round grain shapes and anisotropic grain growth. The density and average grain sizes decreased from 5.84 to 5.54 g/cm<sup>3</sup> and 1.7 to 0.9 µm, respectively, when x increased from 0 to 0.04. The grain size distribution decreased with increased (LiNb)<sup>4+</sup> content. A reduction in the dielectric properties was observed, due to the phase ratio changing away from a morphotropic phase boundary (MPB), an inferior microstructure, and low density caused by (LiNb)<sup>4+</sup> substitution. The (LiNb)<sup>4+</sup> substitution induced the transition from non-ergodic relaxor to ergodic relaxor ferroelectric state.
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    Dielectric and piezoelectric properties near the morphotropic phase boundary for 0.94BNT-0.06BT ceramics synthesized by the solid-state combustion technique
    (2021-01-01)
    Thatawong, Bhoowadol
    ;
    Bhupaijit, Pamornnarumol
    ;
    Lamyai, Yanwarood
    ;
    Vittayakorn, Naratip
    ;
    Bongkarn, Theerachai
    Ceramics of 0.94Bi<inf>0.5</inf>Na<inf>0.5</inf>TiO<inf>3</inf>-0.06BaTiO<inf>3</inf> (0.94BNT-0.06BT) were synthesized by the solid-state combustion technique with various calcination and sintering temperatures (600-800 °C and 1100-1200 °C). A pure perovskite phase was obtained from the powder calcined at 750 °C for 2 h. The phase structure, microstructure, dielectric, ferroelectric and piezoelectric properties of the 0.94BNT-0.06BT ceramics were investigated. The XRD patterns showed coexisting phases of rhombohedral (R) and tetragonal (T) in all samples. Moreover, a good R:T phase ratio of 53:47, as found by Rietveld refinement, good grain growth and high density (5.84 g/cm<sup>3</sup>) were found with a sintering temperature of 1150 °C for 2 h. An excellent maximum dielectric constant (ε<inf>m</inf> = 8405), good ferroelectric properties (P<inf>r</inf> = 28.2 µC/cm<sup>2</sup> and E<inf>c</inf> = 22.1 kV/cm) and a high piezoelectric coefficient (161 pC/N) were observed in this sample, which was near a morphotropic phase boundary (MPB).