Ku-Tak Lee

Dielectric and piezoelectric properties of 0.95(Na0.5K0.5)NbO3-0.05CaTiO3 ceramics with Ag2O contents

Lead-Free ceramics 0.95(Na0.5K0.5)NbO3-0.05CaTiO3-x mol. % Ag2O have been fabricated as a function of the amount of Ag2O content. NKN-CT ceramics showed the highest piezoelectric properties and ferroelectric properties at the 0.5 mol. %Ag2O content. The NKN-CT-Ag2O0.5 mol. % ceramics show a good performance with piezoelectric constant d33 = 221 ρC/N, kp = 0.38%, respectively. The corresponding Curie temperature and remnant polarization reached 370°C and 22.5 µC/cm2, respectively. These results appear that NKN-CTAg2O ceramics are promising candidate materials for lead-free piezoelectric application.

Piezoelectric Properties of 0.98(Na 0.5 K 0.5 )NbO 3 -0.02Li(Sb 0.17 Ta 0.83 )O 3 +0.01wt%ZnO Ceramics with a Sintering Temperature

We studied sintering temperature to enhance the piezoelectric properties of +0.01wt%ZnO (hereafter NKN-LST+ZnO) lead free piezoelectric ceramics. The synthesis and sintering method were the conventional solid state reaction method and sintering was executed at . We found that NKN-LST+ZnO ceramics at optimal sintering temperature showed the improved piezoelectric properties at the optimal sintering temperature. The NKN-LST+ZnO ceramics show good performance with piezoelectric constant

Electrochemical Properties of (Li 0.5-x Na x La 0.5 )Ti 0.8 Zr 0.2 O 3 Ceramics as Improved Electrolyte Materials for Li-ion Batteries

We fabricated (Li0.5-xNaxLa0.5)Ti0.8Zr0.2O3(LNTLZ)ceramics (0≤x≤0.4) with a perovskite structure via standard solid state synthesis. The influence of Na content on the structural and electrical properties of LNTLZ ceramics was also investigated. During XRD patterns analysis, all of the samples showed orthorhombic structure. The resistance of LNTLZ ceramics decreased as Na content increased, and the maximum activation energy shows 0.56 eV at x=0.4 at room temperature. These results indicated that LNTLZ ceramics are a candidate for use Lithium ion batteries as electrolytes.

The Characterization of Spin Coated ZnO TCO on the Flexible Substrates

This article introduces the characterization of spin coated ZnO transparent conducting oxide on the flexible substrates. As a II-IV compound semiconductor, ZnO has a wide band gap of 3.37 eV with transparent properties. Due to this transparent properties, ZnO materials can be also employed as the transparent conducting electrode materials. Therefore, strong demands have been required for the transparent electrodes with low temperature processing and cheap cost. So, We will investigate the electrical property and optical transmittance of ZnO transparent conducting oxide through the 4-point probe resistivity meter, and ultraviolet-vis spectrometer Lamda 35, respectively.

Low Temperature Sintering Behavior and Giant Dielectric Properties of CuO Doped (Ba0.5Sr0.5)TiO3 Ceramics

The effects of CuO additions on the sintering temperature and dielectric properties of (Ba0.5Sr0.5)TiO3 ceramic have been investigated by employing X-ray diffraction analysis, and dielectric properties measurements. In this research, 1–5 wt% CuO was added to the (Ba0.5Sr0.5)TiO3 powders to reduce the sintering temperature. CuO-doped (Ba0.5Sr0.5)TiO3 ceramics were sintered from 750 to 1350°C to confirm the sintering temperature with various dopants, respectively. It was found that the addition of CuO to (Ba0.5Sr0.5)TiO3 could lower the sintering temperature from 1350 to 1150°C. Moreover giant dielectric permittivity was observed in the 5 wt% CuO doped (Ba0.5Sr0.5)TiO3 ceramics.

Dielectric Properties and AC Conductivity of Ag(Ta,Nb)O3 Ceramics

The ac conductivity and relaxation mechanism in Ag(Ta,Nb)O3 ceramics have been investigated systematically. The formation of the ceramics was checked by an X-ray diffraction (XRD) technique analysis. The dielectric permittivity and the loss tangent of the Ag(Ta,Nb)O3 specimen were measured in a frequency range from 1 to 100 kHz at the various temperature ranges (30–110°C). A study on dielectric properties reveals the electrical relaxation phenomenon occurs in the material. Studies on the frequency and temperature dependence of ac conductivity of the Ag(Ta,Nb)O3 ceramics suggest that conduction process in the material is thermally activated process. In this paper, we will discuss the dielectric properties and the ac conductivities of Ag(Ta,Nb)O3 ceramics in relation to the electrical conduction process.

An Investigation on the Dielectric and Microwave Properties of Ag(Ta,Nb)O 3 Thick Films on the Alumina Substrates

Perovskite niobates and tantalates have been placed on a short list of functional materials for future technologies. This article was investigated ferroelectric materials thick film. In this study, we have fabricated the thick film on the substrates by screen printing method. The thick film were fabricated by the mixed oxide method. The sintering temperature and time were 1,150, 2 hr. The electrical properties of thick film were investigated at 30~100.

A Study on Structural and Electrical Properties of ZnO Thick Films on the Glass Substrate and PET Film

As a II-IV compound semiconductor, ZnO has a wide band gap of 3.37 eV with transparent properties. Due to this transparent properties, ZnO materials can be also employed as the transparent conducting electrode materials. Recently, rapid progress has been made in the field of DSSC (dye sensitized solar cell)area. Therefore, strong demands have been required for the transparent electrodes with low temperature processing and cheap cost. In this paper, we will prepare ZnO thick films on the PET substrates for the electrode applications. We will investigate the structural and microstructure properties through the XRD, and SEM analysis, respectively. Also, we will study the electrical of specimens to apply the conducting electrode.

An Investigation on the Aging Properties of NKN Lead-free Piezoelectric Multi-layer Ceramic Actuators

1 mol% excess lead-free piezoelectric multilayer ceramic actuators were investigated to determine their aging properties. To reduce the thermal aging behavior, we applied a rectified unipolar electric field of 5 kV/mm to the specimen to accelerate the electric aging behavior. By employing a rectified unipolar electric field for the piezoelectric actuators, we could remove undesirable heating from the relaxation current in the motion of the ferroelectric domain. To accelerate the aging test, the applied electric fields had a frequency of 900 Hz. To have enough time for charging and discharging, we employed an accurate time constant to design the equivalent circuit model for the aging tester. To extract exact aging behavior, we measured the pseudo-piezoelectric coefficient before and after the aging process. We also measured the electro-mechanical coupling coefficient, the frequency-dependent dielectric permittivity, and the impedance to compare with fresh and aged specimen.

A Study of the Dielectric Properties of the Silver-Tantalate-Niobate Thick Films

Low loss perovskite niobates and tantalates have been placed on a short list of functional materials for future technologies. In this study, we fabricated Ag(Ta,Nb) thick films on the substrates by the screen printing method. The Ag(Ta,Nb) powders were fabricated by the mixed oxide method. The sintering temperature and time were and 2 hrs, respectively. The results of XRD analysis showed that the specimens employed in this study had the pesudo cubic structure. The dielectric permittivity and loss tangent of the films have been characterized from 1 kHz to 1 MHz. Also the dielectric permittivity and loss tangent were measured from 303 K to 393 K. The electrical properties of the film are also discussed.