We investigated the structure of an ultra-thin insulating board with low thermal conductivity along z-axis, which was based on the idea of void layers created during the glass infiltration process for the zero-shrinkage low-temperature co-fired ceramic (LTCC) technology. An alumina and four glass powders were chosen and prepared as green sheets by the tape casting method. After comparison of the four glass powders, bismuth glass was selected for the experiment. Since there is no notable reactivity between alumina and bismuth glass, alumina was selected as the supporting additive in glass layers. With 2.5 vol% of alumina powder, glass green sheets were prepared and stacked alternately with alumina green sheet to form the ‘alumina/glass (including alumina additive)/alumina’ structure. The stacked green sheets were sintered into an insulating substrate. Scanning electron microscopy revealed that the additive alumina formed supporting bridges in void layers. The depth and number of the stacking layers were varied to examine the insulating property. The lowest thermal conductivity obtained was 0.23 W/mK with a 500-㎛-thick substrate.

Pb(Zr, Ti)O₃ (PZT) is a piezoelectric material applied in a typical actuator and has been actively studied. However, in order to overcome the limitations of PZT, piezoelectric ceramics comprising mixed solid solutions of PZT with various relaxer electric materials have been studied. The Pb(Zn_1/3Nb_2/3)-Pb(Ni_1/3Nb_2/3)-Pb(Zr, Ti)O₃ (PZN-PNN-PZT) piezoelectric ceramic, known to have high piezoelectric constant and electromechanical coupling coefficient, was studied herein. The piezoelectric characteristics with various Zr contents (Zr/Ti ratios), PZN molar ratios, and sintering temperatures were compared. The piezoelectric properties of d₃₃＝580 pC/N and kP＝0.68 were obtained with the 0.1PZN-0.2PNN-0.7PbZr_0.46Ti_0.54O₃ composition sintered at 1,290℃.

In this study, the thermal degradation properties of polyethylene terephthalate film has been examined by the capacitance, Tan δ, thermography, FTIR, and SEM results at temperatures of 90~170℃ and frequencies of 0.3~3,000 kHz. It was found that the capacitance decreased with increasing thermal imaging temperature, probably caused by weakening of chemical bond with increasing temperature. Tan δ decreased upon increasing temperature from 90℃ to 170℃, probably due to the molecular motion of COOH radical or OH radical. The FT-IR measurement reveals that no structural change of the material occurs upon thermal radiation. The SEM measurement shows that the material is stabilized by thermal decomposition with increasing temperature; however, excessive thermal degradation obstructs the stabilization of the material.

The amount of electric power for photovoltaic power generation depends on the location of the power plant and the direction of solar cell. The solar cell controls the generation of solar power plants. Therefore, the structure of solar cell, manufacturing method, and optic technology were factors contributing to increased solar cell efficiency; however, the technical limit has been reached. Herein, we propose a new method to increase the solar cell efficiency using a wavelength conversion technology that converts ultraviolet and infrared rays, which are not effectively used in solar cells, into effective wavelength of solar cell. We used fluoride Na(Ca)YF₄ phosphor for wavelength conversion. Then, a wavelength-conversion fluorescent paste, prepared using an organic-silicon binder, was used to prepare a film that was applied to Si solar cells. It was confirmed that conversion efficiency improved by 5% or more.

Effective surface area and morphology of a sensitive thin film are important factors for its applications in sensor systems for the analysis of physical properties. In this study, we investigated the morphologies, electrochemical properties, and applicability of zinc oxide multilayer thin films fabricated by electrodeposition and annealing. The microstructure and electrochemical properties of the zinc oxide films were dependent on temperature and applied voltage. The best characteristics were obtained at an applied voltage of -1.4 V and a temperature of 50℃. The morphologies also changed upon annealing. The results suggest that the zinc oxide films fabricated by electrodeposition and annealing can be applied as various sensor materials.

New white-light-emitting SrSnO₃:Dy³⁺ phosphors were prepared using different concentrations of Dy³⁺ ions via a solid-state reaction. The phase structure, luminescence, and morphological properties of the synthesized phosphors were investigated using X-ray diffraction analysis, fluorescence spectrophotometry, and scanning electron microscopy, respectively. All the synthesized phosphors crystallized in an orthorhombic phase with a major (020) diffraction peak, irrespective of the concentration of Dy³⁺ ions. The excitation spectra were composed of a broad band centered at 298 nm, ascribed to the O^2--Dy³⁺ charge transfer band and five weak bands in the range of 350~500 nm. The emission spectra of SrSnO₃:Dy³⁺ phosphors consisted of three bands centered at 485, 577, and 665 nm, corresponding to the ⁴F_9/2→⁶H_15/2, ⁴F_9/2→⁶H_13/2, and ⁴F_9/2→⁶H_11/2 transitions of Dy³⁺, respectively. As the Dy³⁺ concentration increased from 1 to 15 mol%, the intensities of all the emission bands gradually increased, reached maxima at 15 mol% of Dy³⁺ ions, and then decreased rapidly at 20 mol% due to concentration quenching. The critical distance between neighboring Dy³⁺ ions for concentration quenching was calculated to be 9.4 Å. The optimal white light emission by the SrSnO₃:Dy³⁺ phosphors was obtained when the Dy³⁺ concentration was 15 mol%.

We studied the performance enhancement of organic light-emitting diodes (OLEDs) using 2,3,5,6-fluoro-7,7,8,8-tetracyanoquinodimethane (F₄-TCNQ) as the hole-transport layer. To investigate how F₄-TCNQ affects the device performance, we fabricated a reference device in an ITO (170 nm)/TPD(40 nm)/Alq₃(60 nm)/LiF(0.5 nm)/Al(100 nm) structure. Several types of test devices were manufactured by either doping the F₄-TCNQ in the TPD layer or forming a separate F₄-TCNQ layer between the ITO anode and TPD layer. N,N'-diphenyl-N,N'-di(m-tolyl)-benzidine (TPD), tri(8-hydroxyquinoline) aluminum (Alq₃), and F₄-TCNQ layers were formed by thermal evaporation at a pressure of 10_-6 torr. The deposition rate was 1.0-1.5 Å/s for TPD and Alq₃. The LiF was subsequently thermally evaporated at a deposition rate of 0.2 Å/s. The performance of the OLEDs was considered with respect to the turn-on voltage, luminance, and current efficiency. It was found that the use of F₄-TCNQ in OLEDs enhances the performance of the device. In particular, the use of a separate layer of F₄-TCNQ realizes better device performance than other types of OLEDs.

Transparent ZnS ceramics were synthesized by hydrothermal synthesis (180℃ for 70 h), and were sintered by a hot press process at 950℃. To confirm the optical properties of the ZnS ceramics after sintering for various sintering holding times, we performed X-ray diffraction analysis, scanning electron microscopy, and Fourier-transform-infrared spectroscopy. The ZnS nanopowders was found to be single-phase (cubic) without any hexagonal phase. However, the hexagonal phase is formed and increases in content with increasing sintering holding time. The density of the ZnS ceramics was above 99.7%, except for the unsintered one. The ZnS ceramics showed high transmittance (~70%) when sintered for more than 2 h.

Herein, for the quantitative analysis of the arc beads related to electric fire, we used electron backscatter diffraction (EBSD), a measuring device for grain orientation of materials, we compared and analyzed the surface texture of primary and secondary beads according to the difference in cooling rate at ambient temperature. This analysis revealed that the primary beads showed similar distribution at both low and high angles, while the secondary beads showed a higher distribution at low angles than at high angles. Thus, EBSD can be used for quantitative analysis of the beads and can be applied to identify beads in the future.

We prepared SnS_x thin films on both soda-lime glass (SLG) and molybdenum(Mo)/SLG substrates by a two-step process using a Sn precursor followed by sulfur reaction in rapid thermal annealing (RTA) at different sulfurization temperatures (Ts = 200℃, 230℃, 250℃, and 300℃) and annealing times (t_s = 10 min and 30 min). The single SnS phase was dominant for 200℃≤T_s<250℃, while an additional phase of SnS₂ was appeared at T_s≥250℃ alongside SnS. The SnS grains in all the samples showed strong growth along the preferred [040] direction. The band-gap energy (E_g) of the films was estimated to be 1.24 eV.

Herein we studied the electrical and optical properties of indium tin oxide ITO/Ag/ITO multilayer thin films for application in transparent conducting electrodes. The ITO and Ag thin films were deposited onto soda lime glass (SLG) using radiofrequency and DC-sputtering methods, respectively. The as-synthesized ITO/Ag/ITO multilayer thin films were analyzed using 4-point probe, UV-Visible spectroscopy, and Hall measurement. We observed a rapid increase in electron concentration with increasing Ag thickness. However, electron mobility decreased with increasing Ag thickness. Finally, ITO/Ag/ITO multilayer thin films showed a characteristic low sheet resistance of 18 Ω/sq and high optical transmittance value (80%) with variation of Ag thickness (5~10 nm).

Terahertz time-domain spectroscopy has been used to study the optical properties of Pr³⁺-doped selenide glasses. The complex refractive indexes of Pr³⁺-selenide glasses were measured in a frequency range from 0.3 to 1.5 THz. The real and imaginary refractive indexes increased with increasing frequency and Pr³⁺ ion concentration. The obtained result indicated that the phonon modes of the Pr³⁺-doped selenide glasses shift to lower frequencies with the concentration of Pr³⁺ ions. The theory of far-infrared absorption in amorphous materials was used to analyze the results. The measured data showed that the disorder-induced terahertz absorption increased with increasing Pr³⁺ ion concentration.