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Author: search.filters.author.Vittayakorn, WanwilaiSubject: search.filters.subject.BaZrO3

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    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.
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    High piezoelectric response in the new coexistent phase boundary of 0.87BaTiO3-(0.13-x)BaZrO3-xCaTiO3
    (2015-12-05)
    Sutapun, Manoon
    ;
    Vittayakorn, Wanwilai
    ;
    Muanghlua, Rangson
    ;
    Vittayakorn, Naratip
    An investigation of the coexistent ferroelectric phase was carried out on the ternary system of 0.87BaTiO<inf>3</inf>-(0.13-x)BaZrO<inf>3</inf>-xCaTiO<inf>3</inf> [abbreviated as BT-BZ-xCT (where 0.00≤x≤0.13)]. Temperature-, frequency-dependent dielectric data, electric field-dependent strain and polarization as a function of composition are presented in order to understand the relationships of structure-properties and find the high piezoelectric response in this system. Results showed that ceramics in the composition range of 0.00≤x<0.04 were of a rhombohedral structure and transformed into a tetragonal structure at x>0.06. The multiphase coexistence of the rhombohedral and tetragonal phase in this system was identified at x=0.06. A large, virtually hysteresis-free electric field induced strain of 0.23% was achieved with the composition, x=0.06, at 40kV/cm on the boundary between rhombohedral and tetragonal phase. This relates to an extraordinarily high and normalized piezoelectric coefficient (S<inf>max</inf>/E<inf>max</inf>) of 1280pm/V, which was reached at a low electric field applied at 10kV/mm. These results indicated that a high piezoelectric response may stem primarily from the rhombohedral-tetragonal phase boundary, due to greater lattice softening and reduced energy barriers for polarized rotation.