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Dielectric Relaxation and Microstructures of SnO2 Doped CaCu3Ti4O12 Electroceramics Prepared Via Vibro-milling Method
(2017-01-01)
Makcharoen, Worawut
;
Punsawat, Woratat
High dielectric constant CaCu<inf>3</inf>Ti<inf>4</inf>O<inf>12</inf> (CCTO) is a compound with a high dielectric constant, but it has a high loss tangent at room temperature. This research aims to study on the dielectric properties and loss tangent of SnO<inf>2</inf> doped CaCu<inf>3</inf>Ti<inf>4</inf>O<inf>12</inf> (CCTO) ceramics were investigated. The ceramic samples of SnO<inf>2</inf> doping CCTO were prepared by a solid-state reaction method. The characterization of the samples was carried out using scanning electron microscopy (SEM) and x-ray diffraction (XRD). The conventional solid-state reaction was employed. The metal oxide powders were mixed using a vibratory milling for 6 hour and sintered at 1000°C for 4 hour. The phase formation of the calcined powders and sintered ceramics was examined by X-ray diffraction technique (XRD). Microstructure was examined by scanning electron microscopy (SEM). SnO<inf>2</inf> doping produced a notable decrease in grain size. Average values of grain size, as measured by the linear intercept method. The dielectric measurements at room temperature to 130°C, in the frequency range 100 Hz- 500 kHz. The XRD result a CCTO structure does not changes on Sn doped samples. The results show the loss tangent at room temperature and at 100 kHz decreased from 0.14 for the 0 mol% Sn doped CCTO sample to 0.04 for the 2.0 mol% Sn doped sample while at 500 kHz, it was decreased from 0.2 for the undoped CCTO sample to 0.04 for the 2.0 mol% Sn doped sample. However, the lowest loss tangent was 0.02 at 500 kHz and at 65°C and show a stable loss tangent in temperature range 25 - 130°C.
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Structural, microstructure and electrical properties of La2O3-doped Bi0.5(Na0.68K0.22Li0.1)0.5TiO3 lead-free piezoelectric ceramics synthesized by the combustion technique
(2015-07-01)
Bhupaijit, Pamornnarumol
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Kornphom, Chittakorn
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Vittayakorn, Naratip
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Bongkarn, Theerachai
The effect of firing temperatures on phase formation, microstructure and physical properties of [Bi<inf>0.5</inf>(Na<inf>0.68</inf>K<inf>0.22</inf>Li<inf>0.1</inf>)<inf>0.5</inf>TiO<inf>3</inf>] doped with La<inf>2</inf>O<inf>3</inf> at 0.1 wt% (BNKLLT) ceramics prepared by the combustion method was studied. Glycine was used as fuel and the ratio of raw material (corresponding oxidant metal nitrate) with fuel was about 1:0.56. The samples were calcined at 600-900 °C for 2 h and sintered at 1075-1150 °C for 2 h. The single rhombohedral peroveskite phase of BNKLLT powders was observed from the sample calcined at 750 °C for 2 h. The BNKLLT ceramics exhibited a pure peroveskite phase in all samples. The microstructures of the BNKLLT powders exhibited an agglomerated form while the grain ceramics exhibited a square shape. The average particle size and average grain size increased with increasing firing temperatures. The density, dielectric constant (ε<inf>r</inf> and ε<inf>m</inf>), P<inf>r</inf> and d<inf>33</inf> tended to increase with increasing sintering temperatures up to 1100 °C and then decreased. The maximum density (5.73 g/cm<sup>2</sup>), maximum dielectric constant (ε<inf>r</inf>~2572 and ε<inf>m</inf>~5536), good ferroelectric properties (P<inf>r</inf>~35.78 μC/cm<sup>2</sup> and E<inf>c</inf>~22.42 kV/cm) and highest d<inf>33</inf> (210 pC/N) were obtained by the sample sintered at 1100 °C for 2 h.
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Phase transition behaviour and electrical properties of lead-free (K 0.5Na0.5)NbO3-LiNbO3-LiSbO 3 piezoelectric ceramics
(2011-05-01)
Muanghlua, Rangson
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Niemcharoen, Surasak
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Sutapun, Manoon
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Boonchom, Banjong
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Vittayakorn, Naratip
The ternary system of 0.945(K<inf>0.5</inf>Na<inf>0.5</inf>NbO <inf>3</inf>)-(0.055 - x)LiNbO<inf>3</inf>-xLiSbO<inf>3</inf> [0.945KNN-(0.055 - x)LN-xLS]; x = 0.0-0.055 lead-free piezoelectric ceramics was fabricated by the conventional mixed oxide method with normal sintering. The crystal structure was studied by means of X-ray diffraction (XRD). The results of XRD patterns show that complete solid solutions of the mixed phase between the orthorhombic and tetragonal perovskite phase were observed. The DSC and dielectric data show that the amount of LiSbO<inf>3</inf> in K<inf>0.5</inf>Na<inf>0.5</inf>NbO <inf>3</inf>-LiNbO<inf>3</inf> solid solution slightly decreases the paraelectric cubic-ferroelectric tetragonal phase transition (T<inf>C</inf>) to a low temperature. Furthermore, good dielectric and piezoelectric properties were observed at composition, x = 0.03. The polymorphic phase transition between the orthorhombic and tetragonal phases plays a very important role in enhancement of the piezoelectric properties of KNN-LN-LS ceramics. © 2010 Elsevier B.V. All rights reserved.
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Preparation and properties of lead free bismuth sodium titanate-bismuth zinc titanate ceramics
(2009-12-01)
Muanghlua, Rangson
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Niemcharoen, Surasak
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Vittayakorn, Wanwilai C.
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Tungsitvisetkul, Nattapong
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Chinwaro, Pimjan
Lead-free piezoelectric ceramics based on (1-x)Bi1/2Na1/2TiO3 - x Bi(Zn1/2 Ti1/2)O3 (x = 0.0, 0.02, 0.04, 0.06, 0.08, 0.10, 0.20, 0.30, 0.40, and 0.5) were obtained via solid-state processing techniques. The influence of BZT addition on BNT characteristics, sintering, microstructure and properties was investigated. A single perovskite phase with rhombohedral symmetry was obtained for Bi(Zn1/2Ti1/2)O3 substitutions of up to 10 mole%. A small amount of BZT was effective for improving both sintering behavior and dielectric properties of BNT ceramics. Optimized dielectric properties were obtained for samples with a maximum density of ρ = 98.3% for the composition, x = 0.1. Copyright © Taylor & Francis Group, LLC.
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Effects of strontium on the characteristics of Pb(Zr1/2Ti1/2)O3 - Pb(Zn1/3Nb2/3)O3 ceramics
(2007-08-01)
Vittayakorn, N.
The dielectric and piezoelectric properties of pyrochlore-free lead zirconate titanate-lead zinc niobate ceramics were investigated systematically as a function of Sr doping. The powders of Pb(1-x)Srx[0.7(Zr1/2Ti1/2)-0.3(Zn1/ 3Nb2/3)]O3, where x = 0-0.06 were prepared using the columbite-(wolframite) precursor method. The ceramic materials were characterized using X-ray diffraction, dielectric spectra, hysteresis and electromechanical measurements. The phase-pure perovskite phase of Sr-doped PZN - PZT ceramics was obtained over a wide compositional range. The results showed that the optimized electrical properties were also achieved at composition x = 0.0, which were KP = 0.69, d33 = 670 pC N-1, Pr = 31.9 C cm-2 and rmax = 18600. Maximum dielectric constant values of the systems decreased rapidly with increasing Sr concentration. Moreover, with increasing Sr concentration dielectric constant versus temperature curves become gradually broader. The diffuseness parameter increased significantly with Sr doping. Furthermore, Sr doping has been shown to produce a linear reduction in the transition temperature (Tm) = 294.1-12.7xC with concentration (x). Sr shifts the transition temperature of this system at a rate of 12.7C mol-1%.

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