Journal of Materials Science: Materials in Electronics

Nanostructured materials have the potential to be applied in different areas ranging from electronics to medicine. Techniques for preparation of nanomaterials with a high production rate are essential to make them commercially available. In this work, complex superconducting YBa2Cu3O7−x wires were prepared by using the solution blow spinning technique with different solution injection rates (SIRs): 60, 80 and 100 μL/min. We show that the diameter of the YBCO wires increases from 258 to 954 nm for higher SIRs without any trace of secondary phases as investigated by X-ray diffractograms. Nonetheless, SIR does not supply the real ceramic production rate, which is 4.7 to 33 times higher than the rates of equivalent ceramics produced by Electrospinning. Furthermore, the magnetic properties of the YBCO wires were verified, presenting similar superconducting responses.

A group of (0.65Bi0.5Na0.5–0.35Bi0.2Sr0.7)(Ti1−x,Zrx)O3 (BNBS-(Ti1−x,Zrx)) lead-free energy storage ceramic sheets are prepared by a conventional solid-state sintering method. We find that B-site doping of ZrO2 may minimize the grain size while not change the perovskite structure of BNBS-(Ti1−x,Zrx). As such, BNBS-(Ti1−x,Zrx) possesses the uniform grains and clear grain boundaries, resulting in a high dielectric permittivity (εr) of about 2080 and a low dielectric loss (tanδ) of 0.05 at 100 Hz. Due to the lattice distortion caused by Zr4+ entering the TiO6 octahedral lattice, Tm of BNBS-(Ti1−x,Zrx) decreases with the increase of ZrO2 doping content. Attractively, BNBS-(Ti1−x,Zrx) exhibits relatively slender polarization-electric field (P-E) loops at a high electric field of 100 kV/cm, and BNBS-(Ti0.97,Zr0.03) achieves considerable recycle discharging energy density (Wrec) of 1.47 J/cm3 and high efficiency (η) of 86.94%. Thus, as a block ceramic synthesized by convenient process, this result is superior to most of similar BNT-based materials, and may provide a reference for pulse power capacitors.

We produced the samples that consist of the nominal composition as Sm1.46Ba1.54−xSnxCu3.2Oy (x = 0.35; 0.55; 0.75 and 0.95) by the melt growth method. We investigated Sn-dopant effects regarding differential scanning calorimetry, scanning electron microscope, X-ray powder diffraction and levitation force. The X-ray powder diffraction diagrams show many Sm211 phases in the Sn-doped samples. The lattice structures belong to the orthorhombic and tetragonal unit cells for the Sn-free and Sn-doped samples, respectively. We achieved the reduction of the grain size and the percentage of the orthorhombic phase with Sn doping. The SEM images of Sn-doped samples reveal to the reduction of the grain size. The reason of phase transformation is suspected to be related to the evolution of the c-lattice parameter. It is well-known that oxygen content also causes the phase transformation of the RE123. The a, b, and c-lattice parameters correspond to the unit cell closely matched to the well-known Sm123 values in the literature. The orthorhombic (123) phase in the matrix increases later, even if it makes smaller initially in terms of grain size. In this study, the reduction of the grain size confirms the increasing of tetragonal (211) phase in the matrix. This indicates that the (211) phase has been filtered in the matrix. Namely, the Sn-dopant effect induces the increase of Sm211 phase, in this way the phase transformation occurs in the matrix.

In this paper, we have successfully grown high quality CNT film on FTO substrate followed by ZnO NWs growth on top of CNT film by hydrothermal growth method. Dye-sensitized solar cells (DSSC) were fabricated utilizing carbon nanotube (CNT)/ZnO nanowire (NW) hybrid photoelectrode. By using the CNT/ZnO NWs in DSSC as photoanodes, it was shown that the hybrid structure is promising alternative in conventional DSSCs becuase CNT and ZnO show perfect work-function alignment, high surface area and superior optoelectronic properties. The fabricated DSSC shows a solar cell efficiency of η = 5.55%, which is 20% higher than the cell fabricated without CNT layer. It was demonstrated that the incorporated CNT caused both enhancement of N719-dye absorption on the surface of hybrid structures and significant increase of short circuit current density (Jsc) due to longer electron lifetime. Current density (Jsc)-Voltage characterization indicates the enhancement of the power conversion efficiency of the solar cell mostly due to the increase of carrier density by CNT, decrease in carrier recombination and increase devices voltage. Based on the above results, we were able to obtain almost the highest power conversion efficiency among ZnO based DSSCs.

Indium tin oxide (ITO) thin films were deposited by radio frequency (RF) magnetron sputtering onto glass substrates. The transparent and conducting ITO thin films were obtained on externally unheated glass substrate, without any post-heat treatment, and by varying the deposition process parameters such as the working pressure and the RF Power. The effect of the variation of the above deposition parameters on the structural, surface morphology, electrical, and optical properties of the thin films have been studied. A minimum resistivity of 2.36 × 10−4 Ω cm and 80% transmittance with a figure of merit 37.2 × 10−3 Ω−1 is achieved for the thin films grown on externally unheated substrate with 75 W RF power and 0.5 mTorr working pressure.

A pn junction based on the black Si wafer has been prepared for the photoelectrochemical (PEC) applications by a facile chemical etching method combined with thermal diffusion process. And also in this work, a black Si wafer were fabricated by using a commercial multicrystaline Si (mc-Si) wafer as the raw. It was demonstrated that pn junction was beneficial to enhance the PEC performance of a Si photoanode. The mechanism was further clarified by an electrochemical impedance analysis. The improved PEC activity was attributed to a more efficient charge separation inside the solid electrode. Besides, the p-type Si wafer displayed a characteristic of n-type semiconductor, which was explained through a simple energy band model.

TiO2/AgBr core/shell microspheres have been successfully synthesized via a two-step solvothermal process. The TiO2 core (1.5 µm in average diameter) is coated with a shell (100 nm in average thickness) consisting of AgBr nanoparticles of 6 nm in average size. The composite nanomaterials demonstrate much stronger light absorbance, narrower bandgap, and lower recombination rate of photogenerated electron–hole pairs than both bare TiO2 microspheres and pure AgBr nanoparticles, which endue it with much enhanced photocatalytic activity. The as-prepared TiO2/AgBr photocatalyst exhibits excellent photocatalytic degradation performance towards methylene blue (MB) under visible light irradiation, and 92% MB could be degraded in 90 min, which is much higher than that of bare TiO2 (11%) and pure AgBr (52%). TiO2/AgBr core/shell microsphere photocatalyst also demonstrates good reusability, and the photocatalytic activity has no obvious decrease after five cycles. This study may provide a new insight into the design and synthesis of visible light photocatalytic materials.

Chromium (Cr) doped strontium hexaferrites with nominal composition SrFe12−xCrxO19 (x = 0.0, 0.1, 0.2, 0.3) were prepared using co-precipitation method. Thermal analysis of the samples was carried out using thermogravimetric analysis and differential scanning calorimetry to study the thermal stability as well as the transitions within the samples with variation in temperature. Structural analysis of the samples was carried out using X-ray diffraction (XRD). XRD revealed that all the samples possess hexagonal structure with space group P63/mmc. AC electrical properties including dielectric constant (έ), dielectric loss tangent (tan δ) and ac electrical conductivity (σ ac ) were studied as a function of frequency (1 kHz–3 MHz) at temperatures 100–700 °C. The dielectric losses tend to decrease with increasing Cr content. AC conductivity could be very well explained by Jonscher power law. These materials have applications in high frequency devices with reduced energy losses.