KMITL

Permanent URI for this communityhttps://dspace.kmitl.ac.th/handle/123456789/1

Browse

Settings

Author: search.filters.author.Vittayakorn, NaratipSubject: search.filters.subject.Local structure

Search Results

Now showing 1 - 2 of 2
  • Loading...
    Thumbnail Image
    Some of the metrics are blocked by your 
    consent settings
    Item type:Publication,
    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.
  • Loading...
    Thumbnail Image
    Some of the metrics are blocked by your 
    consent settings
    Item type:Publication,
    Temperature dependent local structure of LiCoO2 determined by in-situ Co K-edge X-ray absorption fine structure (EXAFS)
    (2020-10-01)
    Ekwongsa, Chinawat
    ;
    Rujirawat, Saroj
    ;
    Butnoi, Pichitchai
    ;
    Vittayakorn, Naratip
    ;
    Suttapun, Manoon
    Recently, lithium cobalt oxide (LiCoO<inf>2</inf>) has a great attention as active cathode material lithium ion batteries. In this work, LiCoO<inf>2</inf> powder was prepared by solid state reaction and co-precipitation method. The synthesis parameters and phase formation behavior were investigated in details via several techniques, including thermal analysis, X-ray diffraction (XRD) and scanning electron microscopy (SEM). A change in local structure depending on temperature around Co atoms was investigated using in-situ extended X-ray absorption fine structure (EXAFS). The temperature ranged between 300 °C and 700 °C under air condition was applied for this study.