Soon Ja Park

Influence of ZnO evaporation on the microwave dielectric properties of La(Zn12Ti12)O3

Microwave dielectric properties of the complex perovskite compound La(Zn12Ti12)O3 (LZT) and the effect of ZnO evaporation on the quality factor were examined. The results show that ZnO evaporation was related with the increase in quality factor. The comparison between weight loss and XRD data shows that defects were induced in the samples sintered in air. To investigate the correlation between quality factor and ZnO evaporation, samples sintered in both air and a ZnO atmosphere were examined. The characterization techniques used for this investigation were XRD and TEM. Samples sintered in a ZnO atmosphere have lower quality factor than those sintered in air. The results were compared to the previously reported case of Ba(Zn13Ta23)O3. The variation of quality factor of LZT samples sintered in a ZnO atmosphere was not related to the degree of cation ordering, lattice distortion and second phase.

Preparation of BaTiO3 Thin Films by Metalorganic Chemical Vapor Deposition Using Ultrasonic Spraying

Ferroelectric BaTiO3 thin films were fabricated by metalorganic chemical vapor deposition (MOCVD) at atmospheric pressure. The ultrasonic spraying technique has been used to carry the source materials. The common solutions of barium-diethylhexanoate and diisopropoxy-titanium-bis-acetylacetonate in n-butanol were used as the starting materials. Since the concentration of sources can be controlled in the common solution, this method is more simple and precise than other CVD processes. The films had (110) preferred orientation with increasing temperature. The dielectric constant (e) and the loss factor (tan δ) of thin film deposited at 550° C were about 250 and 0.1, respectively. The leakage current density was 10-5 A/cm2 at 0.1 MV/cm.

Copper oxide-loaded tin dioxide thin film for detection of dilute hydrogen sulfide

The H2S sensing characteristics of SnO2 thin films loaded with CuO were found to be much improved by reducing the film thickness. A 40-nm-thick film showed sensitivity as high as 20000 and 2000 to 1.5 and 0.3 ppm H2S in air, respectively, at 200° C, while the rate of response to 0.3 ppm H2S was rather slow.

Effects of H2O2 on the morphology of ZrO2 powder prepared by ultrasonic spray pyrolysis

Abstract ZrO 2 powder was prepared by ultrasonic spray pyrolysis with H 2 O 2 addition. Powders prepared by zirconyl oxychloride showed a spherical shape and many shell fragments, while the shell fragments disappeared with the addition of H 2 O 2 to the precursor solution. The precursor solution was dried and DTA/TG was performed for the residues in order to investigate the effects of H 2 O 2 . The results show that H 2 O 2 changed the decomposition procedures of the precursor solution.

Electric-field induced strains and pyroelectric coefficients in lead magnesium niobate-lead titanate solid solutions

Abstract In order to understand the electrostrictive behavior of Pb(Mg 1 3 Nb 2 3 )O 3 -PbTiO 3 (PMN-PT ) solid solutions, the dielectric constants, the electric field induced strains, the electric-field induced polarization, and the pyroelectric coefficients of (1 − x)PMN-xPT (x = 0.1 ~ 0.4) were investigated in the temperature range −50 °C ~ 200 °C. For x = 0.1 ~ 0.35, where the phase transition is diffuse, the strain has a maxima at the temperature of maximum pyroelectric coefficient (depolarizing temperature) rather than the temperature of maximum dielectric constant (Curie temperature). For x = 0.4, where the phase transition is relatively sharp, the strain decreases monotonically as the temperature increases. Relationships among the above experimental results are discussed.

High temperature electrical conductivity of La1−xSrxFeO3−δ (x>0.5)

Abstract The high temperature electrical conductivity was measured at temperatures between 900°C and 1300°C for La1−xSrxFeO3t-δ with the change of PO2. The data were explained by the equilibrium among FeFe, Fe.Fe, V…O and SŕLa. From the σ-PO2 data and σ- 1/T data with x values, it is considered that oxygen vacancy is fully ionized in p-type region of higher PO2 and in this higher Sr composition range the influence of [V…O] on the electrical conductivity becomes more important compared to that of [Fe.Fe]. In the lower Sr composition range, [Fe.Fe] has the main compensating role in conductivity, whereas [V…O] mainly compensates the electrical conductivity in the higher range.

Tailoring of the preferred orientation and microstructure in the deposition of BaTiO3 thin films using pulsed laser deposition

Abstract In the deposition of BaTiO 3 thin films using pulsed laser deposition, the preferred orientations and microstructures were critically changed with ambient oxygen pressure. In order to tailor the preferred orientation, template layers which were deposited at different oxygen pressure were introduced. These template layers acted as seed layers, and the preferred orientation of entire films was the same as that of the template layer regardless of the oxygen pressure during deposition. Microstructure of the film was not related with the kind of the template layer. It was closely related with the oxygen pressure during the deposition. In the deposition at 10 −5 Torr, films had different preferred orientations according to the kind of a template layer. However, each film had a dense and smooth surface.

Effect of Ambient Gas Pressure on the Preferred Orientation of Barium Titanate Thin Films Prepared by Pulsed Laser Deposition

Barium titanate thin films were deposited by pulsed laser deposition. The effect of ambient gas pressure on the preferred orientations of the films was systematically investigated. Irrespective of the substrate used, the preferred orientation of films deposited without oxygen flow (10-5 Torr) was the (100) equivalent planes which are electrically neutral. The orientation varied with increasing ambient gas pressure. The variation in the film orientations also depended on the type of substrate. An explanation of the cause of variation in the film orientation with the deposition pressure was attempted in relation to the ionic species near the substrate during deposition.

Preparation of zirconia thin films by metalorganic chemical vapor deposition using ultrasonic nebulization

Zirconia (ZrO{sub 2}) thin films were prepared by metalorganic chemical vapor deposition (MOCVD) using ultrasonic nebulization with new source materials, Zr(OBu){sub 4}, Zr(OBu){sub 3}(acac), Zr(OBu){sub 2}(acac){sub 2}, and Zr(OBu)(acac){sub 3}. This process is a simple and economic method to prepare oxide thin films. Zr(OBu){sub 4} was successfully reacted with acetylacetone at a molar ratio of 1:3. Polycrystalline thin films were deposited at a substrate temperature range from 300{degree}C to 550{degree}C. The substitution of alkoxy radicals by acetylacetone made the deposition rate higher and insensitive to substrate temperature. The films deposited below 450{degree}C mostly had a monoclinic structure, and those deposited above 450{degree}C had a tetragonal structure. The measured optical energy band gap of zirconia film was 5.32 eV. {copyright} {ital 1996 Materials Research Society.}

Piezoelectric properties of Nb2O5 doped and MnO2—Nb2O5 co-doped Pb(Zr0.53Ti0.47)O3 ceramics

The effects of Nb2O5 addition and MnO2‐Nb2O5 co-addition on the piezoelectric properties of Pb(Zr0.53Ti0.47)O3 (PZT) ceramics are investigated. When Nb2O5 is added to PZT, the planar coupling factor (Kp) significantly increases but the mechanical quality factor (QM) as well as the electrical quality factor (QE) decreases. When MnO2 and Nb2O5 are co-doped, QM increases remarkably while Kp rarely changes. This increase in QM is ascribed to the domain pinning by Mn as is the case of previously reported MnO2-doped PZT, and the negligible change in Kp is ascribed to the barely changed tetragonality. Even though MnO2-Nb2O5 co-doped PZT shows a smaller induced strain than that of Nb2O5- doped PZT, excellent temperature stability is obtained. It is shown that MnO2‐Nb2O5 co-doped PZT may be a very suitable material for high-power piezoelectric actuators because of its high Kp, QM and QE, its low dielectric constant and its excellent temperature stability.