Narrow Results

High-quality YBa₂Cu₃O_7-x (YBCO) thick films with thickness over 4.0μm were deposited by photo-assisted metal-organic chemical vapor deposition (PhA-MOCVD) technique with high growth rates. Microstructures of YBCO thick films have been systematically investigated by scanning electron microscopy, high-resolution transmission electron microscopy, and selected area electron diffraction techniques. The fabricated YBCO thick films are very dense and single-crystal like with no visible grain boundaries or voids. The high quality of the prepared YBCO thick films was confirmed further by the results of X-ray diffraction analyses and J_c measurements. Thus, these thick YBCO films prepared by PhA-MOCVD technique have promising application potential in fields such as coated conductors.

BaFe₁₂O₁₉ ferrite thick films were screen-printed and sintered at 1150°C under pressure (hot press sintering). The effects of the hot press sintering on the properties of barium hexaferrite thick films were investigated. The X-ray diffraction pattern shows improvement of the (00l) texture under pressure. The porosity size of the hot press sintering samples decreases obviously and the surface compactness is improved as the pressure is increased. The films are quite anisotropic with magnetic easy axis perpendicular to the film plane. The largest remanence ratio achieved is 0.75 under the highest pressure of 4 MPa.

Cadmium-doped zinc oxide nanoparticles were derived by simple chemical co-precipitation route using zinc acetate dihydrate and cadmium acetate dihydrate as precursor materials. The thick films were casted from chemical co-precipitation route prepared nanoparticles by economic facile screen printing method. The structural, morphological, optical and electrical properties of the film were characterized relevant to alcohol vapor sensing application by powder XRD, SEM, UV-VIS and DC conductivity techniques. The response and sensitivity of alcohol (ethanol) vapor sensor are obtained from the recovery curves at optimum working temperature range from 20${}^{\circ }$C to 50${}^{\circ }$C. The result shows that maximum sensitivity of the sensor is observed at 25${}^{\circ }$C operating temperature. On varying alcohol vapor concentration, minor variation in resistance has been observed. The sensing mechanism of sensor has been described in terms of physical adsorption and chemical absorption of alcohol vapors on cadmium-doped zinc oxide film surface and inside film lattice network through weak hydrogen bonding, respectively.

Ferroelectric PbZr_0.6Ti_0.4O₃ (PZT) thick films were fabricated using a combination of screen-printing method and PZT precursor sol coating process (M. Koch, N. Harris, R. Maas, A. G. R. Evans, N. M. White and A. Brunnschweiler, Meas. Sci. Technol.8 (1997) 49; Y. S. Yoon, J. Korean. Phys. Soc.47 (2005) 321). Structural and electrical properties of the PZT thick films with the treatment of sol coating were investigated. The porosity decreased and the densification was enhanced with increasing the number of sol coatings. All PZT thick films showed the typical X-ray diffraction patterns of a perovskite polycrystalline structure. The thickness of all thick films was approximately 60–61 μm. The relative dielectric constant increased and dielectric loss decreased with increasing the number of sol coatings, and the values of the six-layer PZT-6 film were 167.8, 0.78% at 1 kHz, respectively. The remanent polarization and coercive field of the 6-coated PZT-6 thick films were 14.1 μC/cm² and 20.3 kV/cm, respectively.

Polycrystalline MgB₂ samples with 0, 5, 10, and 20 wt% nano-Y-ZrO₂ (YSZ) powder addition were prepared by short time, as little as several minutes, or long time in-situ reaction process. The phases, microstructures and flux pinning behaviors were characterized using X-ray diffractometry (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscope (TEM) and Magnetic Measurements. Results indicated that nano-YSZ particles included in MgB₂ grains. Samples doped with 10wt% YSZ powders showed new record of critical current density J_c as high as 1×10⁶ and 4×10⁶A/cm² in low magnetic fields at 30 and 20K, respectively. However, the J_c drops faster compared to that made by long time sintering samples. It is proposed that the improved J_c in low fields was due to the enhanced density of the sample, which was caused by the YSZ nano-particle inclusion.

High-quality piezoelectric (Ba_0.85Ca_0.15)(Zr_0.1Ti_0.9)O₃ thick films with dense and homogenous microstructures were fabricated at a low sintering temperature (900°C) using a CuBi₂O₄ sintering aid. The 10 μm thick film exhibited a high longitudinal piezoelectric constant d_33,eff of 210 pC/N with estimated unconstrained d₃₃ value of 560 pC/N very close to that in the corresponding bulks. Such excellent piezoelectric effect in the low-temperature sintered (Ba_0.85Ca_0.15)(Zr_0.1Ti_0.9)O₃ thick films is comparable to the case of lead-based PZT thick films, and may be a promising application in lead-free microdevices such as piezoelectric microelectromechanical systems (MEMS).

50 μm-thick (Pb_0.97La_0.02)(Zr_0.92Sn_0.05Ti_0.03)O₃ antiferroelectric (AFE) thick films with different amount of 0.8PbO–0.2B₂O₃ glass additions were fabricated by the screen-printing method on alumina substrate, which was pre-coated with Pt as electrode. The effects of glass additions on dielectric properties and energy storage performance were investigated in details. Due to the enhancement of breakdown strength (BDS) of the specimens by the addition of glass, the energy storage performances of the thick films could be greatly improved. As a result, with 3% glass addition, the BDS of the specimens were as high as 475 kV/cm, the maximum polarization of 34.8 μC/cm² and the maximum recoverable energy storage density of 7.4 J/cm³ were obtained. The results indicated the (Pb_0.97La_0.02)(Zr_0.92Sn_0.05Ti_0.03)O₃ (PLZST) thick films have a promising potential application in capacitors for pulsed power systems.

The BiFeO₃-based film is one of the most promising candidates for lead-free piezoelectric film devices. In this work, the 1 $\mu$m-thick Bi(${\text{Fe}}_{0.93}$${\text{Mn}}_{0.05}$${\text{Ti}}_{0.02}$)O₃ (BFMT) films are grown on the ITO/glass substrate using a sol-gel method combined with spin-coating and layer-by-layer annealing technique. These films display a large saturated polarization of 95 $\mu$C/cm², and a remanent polarization of 70 $\mu$C/cm². Especially, the films are self-poled caused by an internal bias field, giving rise to asymmetric polarization-electric field ($P-E$) loops with a positive shift along the $x$-axis. A stable self-polarization state is maintained during the applied electric field increasing to 1500 kV/cm and then decreasing back. The weak dependence of $P-E$ loops on frequency (1–50 kHz) and temperature (25–125${}^{\circ }$C) indicate that the internal bias field can be stable within a certain frequency and temperature range. These results demonstrate that the self-polarized BFMT thick films can be integrated into devices without any poling process, with promising applications in micro-electro-mechanical systems.