Byung-Ok Park

Perovskite formation and dielectric characteristics of PFW0.2.PFT0.8-x.PFNx system ceramics

Abstract Effects of 20 mol%Pb(Fe2/3W1/3)O3 addition to Pb(Fe1/2Ta1/2)O3-Pb(Fe1/2Nb1/2)O3 perovskite ceramic system on phase formation and frequency-dependent dielectric characteristics were studied. Phase developments of B-site precursors and perovskite system were monitored by X-ray diffraction. Perovskite powders of high phase yields could be prepared using a B-site precursor method. Dielectric spectra of sintered specimen showed typical relaxor behaviors up to certain temperature ranges, followed by anomalous increase in dielectric constants and losses.

Synthesis of CuInGaSe2 nanoparticles by low temperature colloidal route

CIGS nanoparticles were synthesized by a low temperature colloidal route for the absorber layer of photovoltaic devices. The CIGS nanoparticles were prepared by reacting CuI, InI3, GaI3 in pyridine with Na2Se in methanol at 0°C under inert atmosphere. The reaction products of dark red and yellow colors were turned out to be NaI and CIGS nanoparticles, respectively, by ICP-AES and SEM-EDS analyses. Chalcopyrite structure of the CIGS nanoparticles was confirmed by XRD and TEM diffraction patterns. As compared to the particles from Cu0.9In0.8 Ga0.3Se2 ratio, more uniform and smaller nanoparticles were obtained from Cu1.1In0.68Ga0.23Se1.91 stoichiometric ratio. The CIGS nanoparticles were measured to be in the ranges of 5-20 nm. However, tube like CIGS particles with length of several γn and width in the range of 100-300 nm were obtained from Cu0.9In0.8Ga0.3Se2, and Cu0.9In0.7Ga0.4Se2. The morphological change of the CIGS particles seems to be closely related to the ratio of Cu/(In+Ga).

Preparation and dielectric properties of Pb(Fe23W13)O3-Pb(Fe12Ta12)O3 ceramics

Abstract Selected compositions in the Pb(Fe 2 3 W 1 3 )O 3 -Pb(Fe 1 2 Ta 1 2 )O 3 (PFW-PFT) system were synthesized and characterized. In order to reduce the formation of pyrochlore phase(s) and to increase the perovskite phase yield, a mixed-oxide B-site precursor method was used, by which nearly monophasic perovskite powders were attained throughout the system. Weak-field radio-frequency dielectric properties as functions of composition and frequency were examined.

Electrical and optical properties of (Pb0.9La0.1)TiO3 films prepared by the sol–gel method with ultrasound application

(Pb0.9La0.1)TiO3 thin films were deposited onto indium tin oxide-coated glass and Pt/Ti/SiO2/Si substrates by spin coating. One set of the solutions was sonication-treated during the sol preparation, while the other remained untreated for comparison. The results were analyzed in terms of perovskite developments, dielectric constants and losses, polarization behavior, and optical properties. Perovskite formation temperatures became lower by application of the sonication process. Furthermore, dielectric/ferroelectric and optical transmittance properties were improved substantially.

Formation sequences of FeTaO4 and Pb(Fe1/2Ta1/2)O3

Abstract Structure developments of FeTaO 4 (from Fe 2 O 3 and Ta 2 O 5 ) and Pb(Fe 1/2 Ta 1/2 )O 3 (from PbO and FeTaO 4 ) on heat treatments were studied through X-ray spectrum analyses and phase formation sequences are proposed. FeTaO 4 was formed to full content after competition with an unknown phase, whereas Pb(Fe 1/2 Ta 1/2 )O 3 was developed by replacing prior-formed Pb 4 Ta 6 O 19 , Pb 2 Fe 2 O 5 , and unknown phases.

Characterization of ferroelectric ceramics using x-ray diffraction, transmission electron microscopy, and x-ray photoelectron spectroscopy

Ferroelectric ceramic samples of PbTiO3, prepared by a modified oxide-mixing technique, were examined by x-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques for crystalline and microstructural characterization. XRD clearly revealed only a monophasic perovskite of tetragonal symmetry for the reference PbTiO3, which was established to possess both a–a-and a–c-type 90° domains. The inclination was approximately 2° between the two different domains, as observed by high-resolution TEM. Inductively coupled plasma (ICP) analysis, electron probe microanalysis (EPMA), and x-ray photoelectron spectroscopy (XPS) were employed and the ensuing chemical composition results are discussed. The approximate molar ratios of Pb:Ti were 1:1, 1:1.5, and 1:0.8 as obtained by ICP analysis, EPMA, and XPS, respectively. Corrections for the sensitivity factor (SCorr) for Pb 4f, Ti 2p and the substitution of the matrix factors for FTi,Pb, FPb,Ti have been taken into account in obtaining the Pb:Ti ratio of 1:1 by XPS quantification. The sensitivity factor (SKratos) given by the instrumental maker was compared with the theoretical one (STheo) and the result is also discussed.

Effects of ultrasound on perovskite phase developments, microstructures, and dielectric properties of sol-gel-processed PbTiO3 thin films

PbTiO3 thin films were prepared by spin coating of untreated and sonicated sol (from Pb-Ti stock solution) on Si substrates. The films were fired at different temperatures and were analyzed by scanning electron microscopy, X-ray diffraction and atomic force microscopy. Dried gel and thin films prepared through the two different processing routes were compared in terms of phase developments, microstructures, and dielectric properties. Films prepared from the sonicated sol were found to be superior than those from the untreated sol.

Characterization and deposition of Cu 2 ZnSnS 4 film for thin solar cells via sol-gel method

To achieve low-cost and high-efficiency of thin-film solar cells applications, the sol-gel method that can be coated on a large area substrate, obtain homogeneous thin films of high purity was used. We studied structural and optical characteristics versus annealing temperature of Cu2ZnSnS4 which has kesterite structure by substitution low-cost sulfur (S) instead of high-cost selenium (Se). By analyzing XRD patterns, main peak was observed at 2θ =2 8.5 o when Zn/Sn ratio is 0.8/1.2. And when we observed kesterite structure which has orientation of (112) direction, the more annealing temperature increase the bigger strength of (112) direction is. Cu2ZnSnS4 thin film showed characteristics of kesterite structure at 550 o C. And when we calculated lattice constant, a = 5.5047 and c = 11.014 as same JCPDS (Joint Committee on Powder Standards) data measured. We measured optical transmittance to analyze optical characteristics. Optical transmittance was lower than 65 % at visible ray (λ = 380~770 nm).

Characteristics and Deposition of CuInS 2 film for thin solar cells via sol-gel method0

CuInS2 thin films were prepared using a sol-gel spin-coating method. That makes large scale substrate coating, simple equipment, easy composition control available. The structural and optical properties of CuInS2 thin films that include less toxic materials (S) instead of Se, tetragonal chalcopyrite structure. Copper acetate monohydrate (Cu(CH3COO)2 ·H 2O) and indium acetate (In(CH3COO)3) were dissolved into 2-propanol and 1-propanol, respectively. The two solutions were mixed into a starting solution. The solution was dropped onto glass substrate, rotated at 3000 rpm, and dried at 300 o C for Cu-In as-grown films. The as-grown films were sulfurized inside a graphite container box and chalcopyrite phase of CuInS2 was observed. To determine the optical properties measured optical transmittance of visible light region (380~770 nm) were less than 30 % in the overall. The XRD pattern shows that main peak was observed at Cu/In ratio = 1.0 and its orientation was (112). As annealing temperature increases, the intensity of (112) plane increases. The unit cell constant are a = 5.5032 and c = 11.1064 A, and this was well matched with JCPDS card. The optical transmittance of visible region was below than 30 %.

Effects of ultrasound on crystallization behavior and ferroelectric properties of sol–gel-derived Pb(Zr, Ti)O3 thin films

Pb(ZrxTi1� x)O3 (x ¼ 0:4; 0:52; 0:6) thin films were prepared on ITO-coated glass substrates through the sol–gel process. One set of the solutions was sonicated, while the other was untreated and the results are compared. The films were analyzed with respect to perovskite formation and microstructure developments, as functions of the sol-treatment condition as well as compositional change. Additionally, field-dependent polarization behaviors were also investigated. r 2002 Elsevier Science B.V. All rights reserved.