Journal of Electroceramics

The (Bi0.2Na0.2K0.2La0.2Sr0.2)(Ti1-xScx)O3 (BNKLST-xSc) high entropy ceramics (HECs) have been successfully synthesized via a citrate acid method. The effects of Sc-doping on the lattice structure, microstructural morphology, dielectric and energy-storage properties of HECs are comprehensively investigated. The results indicate that although Sc3+ doped at B-site does not alternate the perovskite structure of BNKLST with a single phase, it results in lattice expansion and weakened bonding in TiO6 octahedron. The dielectric constant of BNKLST-xSc is reduced while the dielectric relaxation is enhanced with increasing Sc content x, due to the enhanced structural inhomogeneity in nano-regions. In addition, the lattice structure of BNKLST-0.2Sc exhibits ultra-high thermal stability at 30–300 °C, which achieves the maximum energy storage density of 1.094 J/cm3 with an outstanding efficiency better than 80%, accompanying by the mechanical and dielectric losses as low as ~ 10–3. It is suggested that BNKLST-0.2Sc could be promising dielectric materials in capacitors and energy-storage devices with an excellent combination of ultrahigh power density, high energy density, thermal stability as well as low mechanical and dielectric losses.

Semi-conductors with mobile acceptors or donors show a new type of I-V relations. This paper presents experimental results for solid state devices based on copper oxide, found to be Cu2O, which exhibit these I-V relations. The cells examined are Cu| Cu2O| In and Cu| Cu2O| Ag and similar ones tested at room temperature. The measured I-V relations are different from those reported for the same type of cells in the past, which were explained to be fixed by a Schottky barrier Cu| Cu2O. We find that the I-V relations relax over a long time which we claim is due to ion redistribution. The new I-V relations can then be explained by assuming that Cu2O is a mixed-ionic-electronic-conductor and adopting a theory developed by us in the past and modified to be applicable to the relevant defect model here. In this case the contribution of Schottky barriers is insignificant.

A systematic computational study to demonstrate electric field dependence of electronic properties of Gd doped MoS2monolayer is being reported. Density functional theory (DFT) based calculated were performed using ADF-BAND package to investigate the effects of applied electric field on pure and Gd doped monolayer of MoS2using supercell approach. A detailed analysis of electric field dependence of host and dopant related states in the monolayers was carried out and discussed to explore the possible implications in devices. The findings on the basis of calculated results indicate that band gap of the monolayer decrease with increase in value of applied electric field. A model indicating this behaviour is also reported. It was further revealed that the formation energy of the monolayers exhibits a consistent decrease with increase in electric field.

The piezoelectric thick film of the active component that works at high temperatures for space and aeronautics has been in significant demand. The thick film has great technological importance as its thickness lies between the thin film and bulk material. The application, such as sensors and actuators, require a thickness that is not less than thin film or not more than bulk to be sufficiently powerful and sensitive. While the thick film is exposed to a temperature higher than room temperature, the piezoelectricity and elastic properties should not be degraded. Thus researchers have been investigating high-temperature thick films for the past decade. This review focuses on the detailed study of high-temperature piezoelectric thick films of lead-based and lead-free based materials and their composites, highlighting fabrication methods. Other important areas, such as substrates for thick film properties achieved and targeted applications, are also discussed. This discussion shows that selecting the high-temperature piezoelectric material, fabrication method, substrates, etc., are essential for fabricating a high-temperature piezoelectric transducer.

The change of electrical and lattice dynamical properties of ferroelectric Ca0.6Sr0.4Bi4Ti4O15 (CSBT) ceramics were studied by doping with 0.1 wt.% of CeO2 and MnO2. The loss tangent and the AC conductivity decreased markedly due to the reduction of charge carrier. The activation energy of doped-CSBT increased owing to the reduction of intrinsic defects in the crystal lattice. For doped and pure CSBT, the appearance of thermal hysteresis and the satisfaction of the Cure-Weiss law by the dielectric susceptibility data assigned the first order nature of a ferroelectric phase transition. Especially in ferroelectric phases, the soft optic phonon mode showed the significant softening towards T 1 (at T 1, the square of soft mode frequency $$ \omega_{\text{s}}^2 $$  → 0) and $$ \omega_{\text{s}}^2 $$ was approximately proportional to T 1-T, where T 1 is ~70°C above T C = 672°C, demonstrated a first order displacive nature of a ferroelectric phase transition. The invariance of lattice dynamical feature indicated that the crystal lattice did not influence markedly by the doping ions.

In this paper, ZnO nanorods were synthesized by low cost and simple wet chemical method and used as a highly sensitive acetone gas sensor with detection limit as low as 25 ppb which makes the sensor a promising choice for various applications. The fabricated sensor showed a response value of 1.75 towards 25 ppb acetone at optimum working temperature of 320 °C with a response time of 30s. However, the sensor showed response value of 60 towards 50 ppm acetone with a response time of 15 s. The grown ZnO nanorods were examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD) for morphology and crystallinity characterization. According to the SEM images, freestanding nanorods with mean diameter of 80 nm and mean length greater than 1.5um were obtained with highly preferential c-axis orientation.

Lead titanate nanopowders were fabricated by mechanochemical synthesis from lead oxide and titanium dioxide. The milling process has been carefully investigated by X-ray diffraction and X-ray excited photoelectron spectroscopy. The first traces of perovskite phase were detected after 5 h synthesis. It was found that intermediated phases (Ti10O18 and Pb3O4) have been formed at the early stage of synthesis. The 50 h milling results in single perovskite phase with average crystallite size of 20 nm.