KMITL

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

Browse

Settings

Author: search.filters.author.Kolodiazhnyi, TarasSubject: search.filters.subject.BaZrO3

Search Results

Now showing 1 - 3 of 3
  • Loading...
    Thumbnail Image
    Some of the metrics are blocked by your 
    consent settings
    Item type:Item,
    The tuning of temperature stability in ultralow loss (Ba/Sr) zirconate microwave dielectric
    (2022-01-01)
    Pulphol, Phieraya
    ;
    Vittayakorn, Wanwilai
    ;
    Bongkarn, Theerachai
    ;
    Kolodiazhnyi, Taras
    ;
    Pongampai, Satana
    The ceramic composition of Ba<inf>1-</inf><inf>x</inf> Sr <inf>x</inf> (Zr<inf>0.96</inf>Ga<inf>0.02</inf>Nb<inf>0.02</inf>)O<inf>3</inf>, where x = 0, 0.1, 0.2, 0.4, 0.5, 0.7, 0.9 and 1, was prepared and its crystal structure, microstructure, Raman and dielectric properties are analyzed. As revealed by powder x-ray diffraction analysis, the crystal structure transforms from cubic (Pm-3m) at 0 ≤ x ≤ 0.2 via tetragonal (Cmcm) at 0.2 < x ≤ 0.5 to orthorhombic (Pbnm) at x > 0.5. This is in agreement with the structural transformations previously reported for the Ba<inf>1-</inf><inf>x</inf> Sr <inf>x</inf> ZrO<inf>3</inf> and Ba<inf>1-</inf><inf>x</inf> Ca <inf>x</inf> ZrO<inf>3</inf> solid solution systems. Raman spectroscopy consistently supports these findings. The effects of structural distortion, grain size and density of samples on the microwave dielectric properties are discussed. With increasing Sr content from x = 0 to 0.2, the Q-factor of Ba<inf>1-</inf><inf>x</inf> Sr <inf>x</inf> (Zr<inf>0.96</inf>Ga<inf>0.02</inf>Nb<inf>0.02</inf>)O<inf>3</inf> ceramics drastically decreases from 18,000 to 3,000 at 10 GHz. The ceramics with a temperature coefficient of −1.4 ppm/K, dielectric constant of 37 and Q-factor of 2,900 at the resonant frequency f = 10 GHz was obtained at x = 0.5.
  • Loading...
    Thumbnail Image
    Some of the metrics are blocked by your 
    consent settings
    Item type:Item,
    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.
  • Loading...
    Thumbnail Image
    Some of the metrics are blocked by your 
    consent settings
    Item type:Item,
    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.