Journal of Electroceramics

The preliminary structural and frequency-temperature dependence of dielectric and electrical characteristics of Ba/Zr modified Bismuth ferrite(BiFeO3) i.e.(Bi1-xBax)(Fe1-xZrx)O3; x = 0.05, 0.1, 0.15, 0.20 at room temperature have been reported. The samples are produced in a perovskite rhombohedral structure, according to the X-ray diffraction pattern and analysis of room temperature XRD data. The SEM photographs are useful for the micro-structural view of the synthesized compounds. Dielectric and electrical characteristics across a wide temperature range 25 °C to 300 °C at different frequencies ranging from 1 kHz to 1 MHz have provided many important results including dielectric dispersion, conduction mechanism, relaxation process and ferroelectricity of the prepared samples. The contributions of grains and grain boundaries towards the net resistance and capacitance of the samples are found from the Nyquist plots. The types of conduction mechanism have been studied from ac-conductivity study of the samples. The Ohmic behaviour is verified by the J–E characteristics of the prepared samples, which have a slope closer to 1. The electrical polarization study through hysteresis loops at room temperature confirms the ferroelectric behavior of the studied materials. According to the experimental results obtained here, the synthesized materials could be beneficial as electronic components in the electronic industries.

The ferroelectric memory is not only an ideal memory with clear advantages such as non-volatility, low power consumption, high endurance and high speed writing, but is also the most suitable device for memory embedded applications. Its manufacturing process makes it more compatible with the standard CMOS process than the traditional non-volatile memory process, since it does not require high voltage operation, and the ferroelectric process does not influence the characteristics of the CMOS devices used in logic cells, analog cells and core cells. In the spreading of Intellectual Property (IP) application for the LSI Industry, this embedded application takes on a more important role. In the near future, the ferroelectric memory technology will be taken into reconfigurable devices as programmable interconnect switches besides being used as embedded memories. These ferroelectric memory based reconfigurable devices can be used as Dynamic Programmable Gate Array (DPGA), which are able to be reconfigured from their original logic in a system under an operation mode. New logic circuits will operated with lower power consumption or a resume function by introducing ferroelectric gated transistors or ferroelectric capacitors. Even though ferroelectric memory technology has many advantages, it is not popular yet, since, the conventional semiconductor process degrades the ferroelectric layer easily. The means to prevent degradation of ferroelectric films in the silicon wafer process will also be discussed.

Pure aluminum nitride (AIN) has been successfully sintered to highly translucent form by microwave sintering at 1850°C with a dwelling time of 30–60 minutes. The results showed that the sintering temperature should be at least 1850°C or higher to get reasonable translucency in the AIN sample by the microwave sintering process. On the other hand, the conventional sintering method requires much longer sintering time to obtain a translucent AIN ceramics.

The Micropen™ direct-write technique was used to fabricate ceramic skeletal structures to develop piezoelectric ceramic/polymer composites with 2–2 connectivity for medical imaging applications. A lead zirconate titanate PZT paste with ∼35 vol.% solids loading was prepared as a writing material and the paste’s rheological properties were characterized to evaluate its feasibly for Micropen deposition. A serpentine pattern was designed and deposited in AutoCAD and with a 100 μm pen tip, respectively. After debinding and sintering, the microstructural analysis showed that the ceramic structures were fully densified, with good bonding among layers. Typical single-layer thickness was ∼50 μm, and sintered line width was ∼120 μm. The composites containing 30–45 vol.% PZT were fabricated within 1 cm2 area, with thicknesses ranging from 350 to 380 μm. Their electromechanical and dielectric properties were measured and found similar to that of composites fabricated by other techniques. The k t was ∼0.61, d 33 was 210–320, with Q m of ∼6 and dielectric constant of 650–940.

Monophase polycrystalline SiC, B4C, TiC and their SiC-TiC, SiC-B4C composite sinters with a theoretical density of 97% are characterized by good mechanical and thermal durability as well as a wide range of electrical conductivity values. SiC, which has semiconductor conductivity and negative TCR, was combined with TiC, which has metallic conductivity and positive TCR. Produced in this way resistive elements, within a temperature range from 293 K to 348 K, exhibit a TCR close to zero, and an impedance independent of frequency within a range from 100 Hz to 1 MHz. The combination SiC with 40 wt% of B4C has been produced resistive elements, which are resistive to oxidation. This combination has also completly resistive character, within a range of 100 Hz to 1 MHz. Most of the investigated materials are suitable for high temperature, noninductive volume resistors.

The introduction of a niobium oxide layer between fluorine-doped tin oxide (FTO) and TiO2 electrodes is known to enhance the power conversion efficiency (η) of dye-sensitized solar cells (DSSCs). Nb thin films were deposited on FTO glass substrates using RF magnetron sputtering. TiO2 pastes were then screen-printed onto the Nb thin films. The multilayered structures were annealed at 500 °C in a muffle furnace and assembled with Pt counter electrodes for DSSC performance evaluation. The Nb thin films were oxidized during the calcination process, producing a post-oxidized layer that increased the solar-cell efficiency by about 15 % and the photocurrent density by approximately 25 %.

Lanthanide elements doped PbTiO3 thin films were prepared by a modified sol-gel method via spin-coating on platinized silicon substrates. The films microstructure and phase composition were investigated by means of scanning electron microscopy, X-ray diffractometry and Raman spectroscopy. Small signal dielectric properties of the films were characterized at different temperatures and doping element concentration. It is shown that dielectric constant, loss tangent and Curie transition temperature of lanthanide elements doped thin films correlate with concentration and ionic radii of these elements. The results obtained are discussed from the point of view of substitution type and compared to some extent to the data, reported by other research groups.

Li2ZrO3-modified LiNi0.5Mn0.5O2 materials with improved electrochemical performance were directly synthesized by a simple mechanical milling route with ZrO2, Li2CO3 and Ni0.5Mn0.5(OH)2 precursors and a high temperature calcination in air atmosphere. The influences of ZrO2 contents on the microstructures and electrochemical properties of LiNi0.5Mn0.5O2 electrode materials were investigated through X-Ray diffraction, scanning electron microscope, energy dispersive spectroscopy and electrochemical tests. The results showed that ZrO2 can be completely converted into Li2ZrO3 in the form of a coating layer covering the surface of LiNi0.5Mn0.5O2 after a heat treatment process. Li2ZrO3 coating can be formed and dispersed homogenously on the surface of 1 mol% Li2ZrO3-modified LiNi0.5Mn0.5O2 materials. The electrochemical tests confirmed 1 mol% Li2ZrO3-modified LiNi0.5Mn0.5O2 materials exhibited the best discharge capacity of 158.3 mAh g−1 after 100 cycles between 2.75 and 4.35 V at 0.2 C, with an excellent capacity retention of 97.2% and higher discharge capacity at −20 °C than that of the pristine LiNi0.5Mn0.5O2. The enhanced cycling stability and low temperature performance may be attributed to the remarkable synergistic effects of Li2ZrO3 protective layer and its homogeneous distribution on LiNi0.5Mn0.5O2 surface with low Li/Ni cation mixing, high electric conductivity and good structure stability.