The low-temperature coefficient of resistance (TCR) is a crucial factor in the development of space-grade resistors for temperature stability. Consequently, extensive research is underway to achieve zero TCR. In this study, resistors were deposited by co-sputtering nickel-chromium-based composite compositions, metals showing positive TCR, with SiO2, introducing negative TCR components. It was observed that achieving zero TCR is feasible by adjusting the proportion of negative TCR components in the deposited thin film resistors within certain compositions. Additionally, the correlation between TCR and deposition conditions, such as sputtering power, Ar pressure, and surface roughness, was investigated. We anticipate that these findings will contribute to the study of resistors with very low TCR, thereby enhancing the reliability of space-level resistors operating under high temperatures.
This study investigated the influence of the viscoelastic property of slag when producing glass fiber, MFS631 with 60% of manganese slag, 30% of steel slag, and 10% of silica stone. To fabricate the MFS631 glass bulk, slag materials were placed in an alumina crucible, melted at 1,550℃ for 2 h, and then annealed at 600℃ for 2 h. It was found that glass is non-crystalline through X-ray diffraction analysis. MFS631 fiber was produced at speed in the range of 100~300 rpm at 1,150℃. The loss modulus (G″) and storage modulus (G′) of the produced glass fiber were evaluated at high temperatures. G′ and G″ of MFS631 were greater than 893℃, and the modulus value was 136,860 pa. This is similar to the results of a general E-glass fiber graph. Therefore, it was concluded that its spinnability is similar to that of E-glass fiber; therefore, it can be commercialized.
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.
In this study, in order to develop composition ceramics for refrigeration device application at a temperature of less than 90°C, a Ba(Ti1-xZrx)O3 composition was fabricated using a conventional solid-state method. Electrocaloric properties of these ceramics were investigated using the characteristics of P-E hysteresis loops in a wide temperature range from room temperature to 150°C. The Curie temperature of Ba(Ti1-xZrx)O3 ceramics decreased with the increase of x. The maximum value of □T = 0.07°C in an ambient temperature of 85°C under 30 kV/cm appeared when x = 0.125. It was concluded that the composition (x = 0.125) ceramics can be used for refrigeration device applications.
In this study, in order to develop composition ceramics for refrigeration device application, Ba(Ti0.9Zr0.1)O3 composition was fabricated using conventional solid-state method. Electrocaloric effect of this ceramic was investigated using the characteristics of P-E hysteresis loops at wide temperature range from room temperature to 150℃. Curie temperature of Ba(Ti0.9Zr0.1)O3 ceramics showed 80℃. The maximum value of ?T = 0.12℃ in ambient temperature of 115℃ under 30 kV/cm was appeared. It is concluded that Ba(Ti0.9Zr0.1)O3 ceramics can be applied as refrigeration device application.
In this study, the effect of vanadium oxide (V2O5) content and pre-sintering atmosphere on sealing property of glass frit that consisted of V2O5-BaO-ZnO-P2O5-TeO2-CuO-Fe2O3 SeO2 was investigated by XPS (X-ray photoelectron spectroscopy). The content of V2O5 was changed to 15, 30, and 45 mol%, and the pre-sintering was carried out in air and N2 condition, respectively. XPS analysis conducted before and after laser irradiation with identical sample. Before laser treatment, glass frits that were pre-sintered at air condition showed both V4+and V5+, but the valence state was changed to V5+ after laser irradiation when the glass frits contained 30 and 45 mol% V2O5; this change led to non-adhesive property. On the other hand, glass frits that were pre-sintered at N2 condition exhibited only V4+ and it showed fine adhesion irrespective of the V2O5 content. As a result, the existence of V4+ seems to be a major factor for controlling the adhesive property of glass frit for laser sealing.
[(Co1-xCux)0.2(Ni0.3Mn0.7)0.8]3O4 (0≤x≤1) thin films prepared by metal organic decomposition process were fabricated on SiN/Si substrate for infrared sensor application. Their structural and electrical properties were investigated with variation of Cu dopant. The [(Co1-xCux)0.2(Ni0.3Mn0.7)0.8]3O4 (CCNMO) film annealed at500℃ exhibited a dense microstructure and a homogeneous crystal structure with a cubic spinel phase. Theircrystallinity was further enhanced with increasing doped Cu amount. The 120 nm-thick CCNMO (x=0.6) thin film had a low resistivity of 53 Ω·cm at room temperature while the Co-free film (x=1) showed a significantly decreased resistivity of 5.9 Ω·cm. Furthermore, the negative temperature coefficient of resistance(NTCR) characteristics were lower than -2%/℃ for all the specimens with x≥0.6. These results imply that the CCNMO (x≥0.6) thin films are a good candidate material for infrared sensor application.
Copper manganite thin films were fabricated on SiNx/Si substrate by metal organic decomposition (MOD) process. They were burned-out at 400℃ and annealed at various temperatures (400∼800℃) for 1h in ambient atmosphere. Their micro-structure and negative temperature coefficient of resistance (NTCR) characteristics were analyzed for micro-bolometer application. The copper manganitefilm with a cubic spinel structure was well developed at 500℃ which confirmed by XRD and HRTEM analysis. It showed a low resistivity (47.5 Ω·cm) at room temperature and high NTCR characteristics of-4.12%/℃ and -2.15%/℃ at room temperature and 85℃, implying a good thin film for micro-bolometer application. Furthermore, its crystallinity was enhanced with increasing temperature to 600℃. However, the appearance of secondary phase at temperatures higher than 600℃ lead to deteriorate the NTCR characteristics.
Thin thermistor films of solutions with nickel and manganese oxides were prepared by metal-organic decomposition (MOD). The structural properties of the thin films were investigated as a function of annealing temperature. Field emission scanning electron microscope (FE-SEM) results indicated that the thin films had a thin thickness, smooth and dense surface. The crystallization temperature of 414.9℃ was confirmed from thermogavimetric-differential thermal analysis (TG-DTA)curve. A single phase of cubic spinel structure was obtained for the thin film annealed from 700℃ to 800℃,which was confirmed from the X-ray diffraction (XRD). From the selected area electron diffraction(SAED) in high resolution transmission electron microscope (HRTEM), the nano grains (2∼3 nm) of spinel phase with (311) and (222) planes were detected for the thin film annealed at 500℃, which could be applicable to read-out integrated circuit (ROIC) substrate of the uncooled microbolometer with low processing temperature.
The front electrode should be used to make solar cell panel so as to collect electron. The front electrode is used by paste type, printed on the Si-solar cell wafer and sintered at about 800℃. The paste is composed Ag powder and glass frit which make the ohmic contact between Ag electrode and n-type semiconductor layer. From the previous study, the Ag electrodes which used two commercial glass frit of Bi-system were so different on the interface resistance. The main composition of them was Bi-Zn-B-Si-O and few additives added in one of them. In this study, glass frit was made with the ratio of Bi2O3 and ZnO on the main composition, and then paste using glass frit was prepared respectively. And, also, the paste using the glass frit added oxide additives were prepared. The change of interface resistance was not large with the ratio of Bi2O3 and ZnO. In the case of G6 glass frit, 78 wt% Bi2O3 addition, the interface resistance was 190 Ω and most low. In the glass frit added oxide, the case of Ca increased over 10 times than it of G6 glass frit on the interface resistance. It was thaught that after sintering, Ca added glass frit was not flowed to the interface between Ag electrode and wafer but was in the Ag electrode.
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