Browsing by Author "Chou, Chen-Chia"

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Correlation of Microstructures and Conductivities of Ferroelectric Ceramics Using Complex Impedance Spectroscopy
(2010-06-01)
Chen, Pin-Yi
;
Chou, Chen-Chia
;
Tseng, Tseung-Yuen
;
Chen, Haydn
;
電子工程學系及電子研究所
The microstructures and conductivities of lead-free ceramics [Bi(0.5)(Na(1-x)K(x))(0.5)]TiO(3) with x = 0.18 (BNKT) and lead-based ceramics of x(0.94PbZn(1/3)Nb(2/3)O(3) + 0.06BaTiO(3)) + (1 - x)PbZr(y)Ti(1-y)O(3) with x = 0.5, y = 0.52 (PBZNZT) were investigated. Experimental results show that the activation energy of grain boundary conductivity is higher than that of grain conductivity for the BNKT system, indicating that the Bi(2)O(3) evaporation of grains induces an easy conduction path through grains. However, the activation energy of grain boundary conductivity is lower than that of grain conductivity for the PBZNZT system, which might be attributed to the charged particles in the amorphous phase at grain boundaries, participating in the conduction process. A conduction model of both grain and grain boundary conductivities was proposed, and the microstructural characteristics and AC impedance data of ferroelectric ceramics correlate fairly well, suggesting that impedance spectroscopy is an efficient characterization technique for the grain boundary engineering of ferroelectric ceramics. (C) 2010 The Japan Society of Applied Physics DOI: 10.1143/JJAP.49.061505
Dependence of ferroelectric characteristics on the deposition temperature of (Pb,Sr)TiO3 films
(2007-10-01)
Wang, Jyh-Liang
;
Lai, Yi-Sheng
;
Shye, Der-Chi
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Chou, Chen-Chia
;
Chiou, Bi-Shiou
The pulsed laser deposition (PLD) of (Pb,Sr)TiO3 (PSrT) films on Pt/SiO2/Si at low substrate temperatures (T-s, ranging from 300 to 450 degrees C, has been investigated. The PLD PSrT films prepared at low Ts exhibit ferroelectric proper-ties, good crystallinity, and no significant interdiffusion between the PSrT film and the Pt bottom electrode. The conduction mechanism is identified as Schottky emission at low electric fields and as Poole-Frenkel emission at high electric fields. PSrT films grown at appropriate T, yield fewer interface states and fewer trapping states, leading to a smaller leakage current. The enhanced (100) preferred orientation of PSrT films deposited at T-s= 350-400 degrees C exhibits optimum ferroelectricity. In addition, the dielectric constant and ferroelectricity are associated with the preferred orientation. This shows that the electrical characteristics strongly rely on the preferred orientation and trapping states, which could be controlled by varying the substrate temperature (T, <= 450 degrees C during PLD.
Effects of Second Phase and Defect on Electrical Properties in Bi0.5Na0.5-xKxTiO3 Lead-Free Piezoelectric Ceramics
(2011)
Chen, Pin Yi
;
Chen, Cheng Sao
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Chou, Chen-Chia
;
Tseng, Tseung-Yuen
;
Chen, Haydn
Second phase and defect formation mechanism of (Bi-0.5(Na1-xKx)(0.5))TiO3 (BNKT100x) ceramics were investigated using electron microscopy, x-ray photoelectron spectroscope (XPS) and electrical properties measurements. Experimental results indicated that second phase formation induces Bi-rich regions and compositional inhomogeneity within matrix due to thermodynamic stability of potassium titanate. Ti valence transition for BNKT ceramics sintered in air might be ascribed to formation of the secondary phase, rather than simply attributed to volatilization of bismuth. Li substitution at A-site in BNKT ceramics suppresses formation of the second phase and Ti valence transition. Appropriate Li doped BNKT ceramics suppress oxygen vacancies and titanium valence transition, and therefore decrease the leakage current.
Preface
(2017-01-01)
Tuan, Wei-Hsing
;
Chou, Chen-Chia
;
Tseng, Tseung-Yuen
;
Wang, Sea-Fue
;
Tseng, Wen-Jea
Second Phase and Defect Formation in Bi(0.5)Na(0.5-x)K(x)TiO(3) Ceramics
(2010-06-01)
Chen, Pin-Yi
;
Chou, Chen-Chia
;
Tseng, Tseung-Yuen
;
Chen, Haydn
;
電子工程學系及電子研究所
The second phase and defect formation mechanisms of [Bi(0.5)(Na(1-x)K(x))(0.5)]TiO(3) (BNKT100x) ceramics were investigated using electron microscopy, X-ray photoelectron spectroscopy (XPS), and electrical properties measurement. Experimental results indicated that second phase formation induces Bi-rich regions and compositional inhomogeneity within the matrix owing to the thermodynamic stability of potassium titanate. The Ti valence transition for BNKT ceramics sintered in air might be ascribed to the formation of secondary phase and low oxygen atmosphere, rather than simply attributed to the volatilization of bismuth. Li substitution at the A-site in BNKT ceramics suppresses formation of the second phase and Ti valence transition. Appropriate atmosphere control during material processing, such as sintering at higher oxygen pressure, and post oxidization annealing suppress oxygen vacancies and titanium valence transition, and therefore decrease the leakage current as well as improve electrical properties. (C) 2010 The Japan Society of Applied Physics DOI: 10.1143/JJAP.49.061506
Second Phase and Defect Formation in Bi0.5Na0.5-xKxTiO3 Ceramics
(2010-06-01)
Chen, Pin-Yi
;
Chou, Chen-Chia
;
Tseng, Tseung-Yuen
;
Chen, Haydn
;
電子工程學系及電子研究所
The second phase and defect formation mechanisms of [Bi-0.5(Na1-xKx)(0.5)]TiO3 (BNKT100x) ceramics were investigated using electron microscopy, X-ray photoelectron spectroscopy (XPS), and electrical properties measurement. Experimental results indicated that second phase formation induces Bi-rich regions and compositional inhomogeneity within the matrix owing to the thermodynamic stability of potassium titanate. The Ti valence transition for BNKT ceramics sintered in air might be ascribed to the formation of secondary phase and low oxygen atmosphere, rather than simply attributed to the volatilization of bismuth. Li substitution at the A-site in BNKT ceramics suppresses formation of the second phase and Ti valence transition. Appropriate atmosphere control during material processing, such as sintering at higher oxygen pressure, and post oxidization annealing suppress oxygen vacancies and titanium valence transition, and therefore decrease the leakage current as well as improve electrical properties. (C) 2010 The Japan Society of Applied Physics DOI: 10.1143/JJAP.49.061506
Structural and electrical investigations of pulse-laser-deposited (Pb,Sr)TiO3 films at various oxygen partial pressures
(2007)
Wang, Jyh-Liang
;
Lai, Yi-Sheng
;
Liou, Sz-Chian
;
Chou, Chen-Chia
;
Tsai, Chun-Chien
Pulsed-laser deposited (Pb,Sr)TiO3 (PSrT) films on Pt/SiO2/Si substrate deposited at various oxygen partial pressures (P-O2), ranging from 50 to 200 mTorr, were investigated in this work. PSrT films exhibit (100) preferred orientation at lower P-O2 and then transit to (110) preferred orientation above 100 mTorr. The paraelectricity/ferroelectricity transition and dielectric constant of PSrT films are associated with the preferred orientation and oxygen concentration at various P-O2. Furthermore, films deposited at higher P-O2 exhibit higher breakdown field and smaller leakage current density as a consequence of fewer oxygen vacancies. Except for the case of films deposited at 200 mTorr, the conduction mechanism is identified as Schottky emission/Poole-Frenkel emission at low/high electric fields. (c) 2007 The Electrochemical Society.
Temperature-dependent characteristics of pulse-laser-deposited (Pb,Sr)TiO3 films at low temperatures
(2008-01-01)
Wang, Jyh-Liang
;
Lai, Yi-Sheng
;
Chiou, Bi-Shiou
;
Chou, Chen-Chia
;
Lee, Trent Gwo-Yann
Pulsed laser deposition (PLD) of (Pb,Sr)TiO3 (PSrT) film on Pt/SiO2/Si at low substrate temperatures (T-s), ranging from 300-450 degrees C, has been investigated. As T-s increases, the films reveal coarsening clusters, improved crystallization of the perovskite phase, distinct capacitance-electric field (C-E) hysteretic loops and a larger dielectric constant. The 350 degrees C-deposited film shows strong (100) preferred orientation and optimum dielectric properties with the dielectric constant of similar to 620. The current density increases as the measurement temperature and the electric field increase. Moreover, PSrT films exhibit a strong negative temperature coefficient of resistance (NTCR) behavior at temperatures ranging from 100 to 390 degrees C.
Thermal stability and electric properties of Ba0.7Sr0.3TiO3 parallel plate capacitor with nano-Cr interlayer
(2006-12-20)
Ho, Chia-Cheng
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Chiou, Bi-Shiou
;
Chang, Li-Chun
;
Chou, Chen-Chia
;
Liou, Bo-Heng
A novel sandwich structure of Ba0.7Sr0.3TiO3/Cr/Ba0.7Sr0.3TiO3 (BST/Cr/BST) was sputtered onto Pt/Ti/SiO2/Si substrate. With the insertion of a Cr layer, the leakage currents are decreased and the thermal stability of the specimens is enhanced. Temperature coefficient of capacitance (TCC) of specimens with BST(200 nm)/Cr(2 nm)/BST(200 nm) multifilms can achieve about 83% lower than those with BST (400 nm) monolayer. However, the dielectric constant of the BST(200 nm)/Cr(2 nm)/BST(200 nm) multifilms decreases to about 37% of that BST monolayer. The leakage current densities under an electric field of 125 kV/cm at 90 degrees C are 4 x 10(-4) A/cm(2) and 9 x 10(-1) A/cm(2) for BST(200 nm)/Cr(2 nm)/BST(200 nm) and monolayer BST (400 nm), respectively. X-ray diffraction results indicate the formation of a CrO3 secondary phase after annealing at 700 degrees C or above in O-2 atmosphere. The root causes for the improvement of leakage currents and thermal stability with the insertion of nano-Cr interlayer are explored. The results show the insertion of Cr-nanolayer improves the electric properties for application in capacitors. (c) 2006 Elsevier B.V All rights reserved.