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Author: search.filters.author.Charoonsuk, ThitiratSubject: search.filters.subject.BaZrO3

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    The modification of surface, size and shape of barium zirconate powder via salt flux
    (2019-01-01)
    Charoonsuk, Thitirat
    ;
    Kolodiazhnyi, Taras
    ;
    Vittayakorn, Naratip
    The “top-down” process via direct conversion of the micro (μm)-to-submicroscale (sub-μm) particle was applied in this work by using eutectic chloride salts to prepare BaZrO<inf>3</inf>. The particle size at optimum condition could be decreased by more than 10 times from 2.1 ± 0.9 μm to 168 ± 23 nm without destroying the 1:1 of Ba:Zr stoichiometry. The uniform sub-μm-BaZrO<inf>3</inf> powder was sintered in order to obtain ~98% dense ceramic at 1400°C/10 h, which is significantly lower than the 1650°C in normal cases. The microwave dielectric constant, tan δ, and quality factor were also determined. Furthermore, this method also was applied to lead-free piezoelectric material in the 0.87BaTiO<inf>3</inf>–0.13BaZrO<inf>3</inf>–CaTiO<inf>3</inf>(0.87BT–0.13BZ–CT) system. The particle size of 0.87BT–0.13BZ–CT was reduced greatly from >10 µm to 2.8 ± 0.4 µm. It can be proved that salt flux dissolution method enables high-purity with uniform sub-micro/nanometer powder production in one step by using simple laboratory equipment and low-cost raw materials.
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    CaTiO3 induced ferroelectric phase coexistence and low temperature dielectric relaxation in BaTiO3–BaZrO3 ceramics
    (2018-05-01)
    Sutapun, Manoon
    ;
    Charoonsuk, Thitirat
    ;
    Kolodiazhnyi, Taras
    ;
    Vittayakorn, Naratip
    The series of 0.86BaTiO<inf>3</inf>–(0.14−x)BaZrO<inf>3</inf>–xCaTiO<inf>3</inf> (abbreviated as BT–BZ–xCT) ceramics with 0.03 ≤ x ≤ 0.11 were studied to obtain high piezoelectric properties. Rietveld refinement analysis indicated that the BT–BZ–CT compositions follow a gradual rhombohedral (R) → orthorhombic (O) + R → O + tetragonal (T) → T phase transformation with increasing x. Clear evidence of the series of ferroelectric phase transitions was also found in the dielectric results. The R-O and O-T transition temperature shifted close to ambient temperature, while the Curie temperature slightly increased with increasing x. In addition to the dielectric loss peaks associated with the structural phase transitions, a broad low-temperature dielectric loss peak was detected in the R phase at T = 90-150 K. This dielectric relaxation was attributed to the domain wall freezing and fits well to the Vogel-Fulcher model with activation energy E<inf>a</inf> ≈ 60-300 meV and freezing temperature T<inf>VF</inf> ≈ 75-140 K. High piezoelectric strain coefficient (d<inf>33</inf>*) of about 1030 pm/V at 10 kV was achieved at x = 0.07, and a high Curie temperature (T<inf>C</inf>) was maintained at about 375 K.
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    Soft-mechanochemical synthesis of monodispersed BaZrO3 sub-microspheres: Phase formation and growth mechanism
    (2017-03-15)
    Charoonsuk, Thitirat
    ;
    Vittayakorn, Naratip
    Current technological and scientific challenges have encouraged the search for a simple and energy-efficient method to synthesis fine product particles with desirable morphology and properties. The submicro-spheres of perovskite barium zirconate (BaZrO<inf>3</inf>) in this study were synthesized successfully via the soft-mechanochemical method under ambient conditions, without surfactants or any capping agents. The synthetic mechanism model was proposed as being time-dependent. The hydrolysis, nucleation (crystallization) and growth of particles via Ostwald ripening were discussed deeply. Mechanical energy not only afforded a local high temperature to activate the chemical reaction and diffusion rate of particles, but also prevent aggregation and agglomeration by homogeneous mechanical stirring. Nevertheless, as-prepared BaZrO<inf>3</inf> powders exhibited properties of photoluminescence (PL) with green emission from lattice formation defects. Dielectric properties and the quality factor (Q-factor) were investigated as well. It was notable that the soft-mechanochemical method can provide a high yield and enable work that is environmentally friendly.