Niobium oxide(Nb2O5) films were deposited on p-type Si wafers at room temperature using in-line pulsed-DC magnetron sputtering system with various frequencies. The different duty ratios were obtained by varying the frequency of pulsed DC power from 100 to 300 kHz at the fixed reverse time of 1.5 μs. From the thickness of the sputtered NbOx films, it was possible to obtain much higher deposition rate in case of pulsed-DC sputtering than RF sputtering. However, the similar leakage currents and structural characteristics were obtained from the metal-insulator-semiconductor(MIS) structure fabricated with the NbOx films and the x-ray photoelectron spectroscopy(XPS) results in spite of the different deposition rates. From the experimental results, the NbOx films sputtered by pulsed-DC sputtering are expected to be used in the fabrication process instead of RF sputtering.

In this study, in order to develop excellent lead free piezoelectric ceramics for piezoelectric actuators application, Li0.04(Na0.50K0.50)0.96[(Nb0.86Ta0.10Sb0.04)0.994Co0.015]O3+0.0025SrO + 0.15 wt%K2CO3 + x wt%Nb2O5 (x = 0 - 0.5 wt%) (abbreviated as LNKNTSCS-xN) ceramics were fabricated by a conventional sintering technique. the phase structure, microstructure and electrical properties were investigated with a emphasis on the influence of the Nb2O5 content. High electrical properties of d33= 234 pC/N, kp= 0.392, εr= 1,395, ρ= 4.70 g/cm3 were obtained from the specimen with x= 0.4 wt%, which suggests that the composition ceramics is a promising lead-free piezoelectric material.

Multifunctional structures with two kinds of materials have been intensively investigated in order to improve their electrical characteristic with two functions simultaneously. However, the research regarding of multifunctional ceramic sensor is still in a preliminary stage and how to integrate them with low-cost and high-yield mass production process remains a challenge issue. In this study, we fabricated the multifunctional ceramic sensor composed of temperature and gas sensors. Moreover, we investigated the CO sensing properties of three dimensional nanostuctured Nb2O5 thin film gas sensors fabricated with silica (SiO2) nanosphere (Ø= 750 nm). Compared to plain films, the nanostructured films show enhanced gas sensing of greater sensitivity and a faster response. This result reveals that significantly increased sensitivity is an increase in the effective surface area for the adsorption of gas molecules.

In this study, the effect of Nb2O5 and sintering time on the positive temperature of coefficient of resistivity (PTCR) behavior of lead free Ba0.99(Bi0.5Na0.5)0.01TiO3 (BBNT) ceramics were investigated in order to fabricate a PTC thermistor with high Tc temperature more than 140℃. In particular, BBNT ceramic doped with 0.1mol% Nb2O5 and sintered at 1350℃ for 4 h has significantly increased Curie temperature (Tc) of about 200℃, showed good PTCR behavior of room-temperature resistivity (ρrt) of 40 Ω·㎝, a high ρmax/ρmin ratio of 43.78×103 and a large resistivity temperature factor (α) of 16.1%/℃. With increasing addition of Nb2O5 content, the ρrt decreased to a minimum value of 40 Ω·㎝ at 0.1mol% Nb2O5 and the ρrt increased for x value over 0.1 mol%.