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Author: search.filters.author.Kolodiazhnyi, TarasSubject: search.filters.subject.BaTiO3

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    Thermally induced phase transition and dielectric relaxation in lead-free BaTi0.94Sn0.06O3 Ceramics: Insights from in-situ XRD and XAS
    (2025-11-01)
    Sukkha, Usa
    ;
    Chanlek, Narong
    ;
    Kidkhunthod, Pinit
    ;
    Kolodiazhnyi, Taras
    ;
    Vittayakorn, Wanwilai
    Lead-free BaTi<inf>0.94</inf>Sn<inf>0.06</inf>O<inf>3</inf> (BTS) ceramics were synthesized using the conventional solid-state reaction method to investigate thermally induced phase transitions and dielectric relaxation phenomena. A combination of in-situ X-ray Diffraction (XRD) and in-situ Synchrotron X-ray Absorption Spectroscopy (XAS) was employed to examine phase transitions across the temperature range of 200–400 K. The results reveal sequential phase transitions: rhombohedral-orthorhombic (R + O) at 200 K, orthorhombic (O) at 250–300 K, tetragonal (T) at 325–359 K, and tetragonal-cubic (T + C) at 373–400 K. Dielectric measurements highlight an anomalous relaxation behavior at 70–160 K, attributed to domain wall freezing. This phenomenon follows Vogel-Fulcher behavior, with an activation energy of 14 meV, a freezing temperature of 82 K, and an attempt frequency of 4.7 × 10<sup>6</sup> Hz. X-ray Photoelectron Spectroscopy (XPS) analysis reveals oxygen deficiency on the surface of the BTS ceramic, resulting in the coexistence of Ti<sup>3+</sup>/Ti<sup>4+</sup> and Sn<sup>2+</sup>/Sn<sup>4+</sup> oxidation states. These defects significantly influence the dielectric and phase transition properties. This study provides comprehensive insights into the interplay between local structural changes and phase transition mechanisms in BTS ceramics. By employing a multi-technique approach, it advances the understanding of dielectric and ferroelectric behaviors, positioning BTS ceramics as promising candidates for lead-free dielectric and ferroelectric device applications.
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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.