The ground-state structural, electronic, magnetic, optical and dielectric properties of MnTiO3 are calculated using density functional theory within the generalized gradient approximation. The structure parameters obtained agree well with experimental results. The electronic structure results show that the G-type antiferromagnetic phase of LN-type MnTiO3 has an indirect band gap of 0.85 eV. The calculated local magnetic moment of Mn ion is 4.19 μB. The calculated Born effective charges (BECs, denoted by tensor Z*) show that the Z* of Ti and O atoms are significantly and anomalously large. Interestingly, ferroelectric spontaneous polarization of large magnitude is predicted to be along [111] direction with a magnitude of 87.95–105.22 μC/cm2. B-site Ti ions in 3 d0 state dominate ferroelectric polarization of multiferroic MnTiO3, whereas A-site Mn ions having partially filled 3 d5 orbitals are considered to contribute to its antiferromagnetic properties. Furthermore, it is predicted that multiferroic MnTiO3 shows good dielectric and optical properties.

Raman scattering spectra and ferroelectric properties of epitaxial tetragonal Pb(Zr, Ti)O3 were investigated for polar axis-oriented thin films with various Zr/(Zr + Ti) ratios and by changing the ratios from 0 to 0.50 at different measurement temperatures. The chosen films in the thickness range of 1–2 μm present the advantage of showing small residual strain. The E (TO) modes were successfully isolated using cross-polarization configurations, while A1 (TO) and B1 modes were activated using parallel polarization configurations. Systematic changes in Raman peak positions were observed with changes in the Zr/(Zr + Ti) ratios at different measurement temperatures. It was found in both cases that the tetragonal distortion (c/a-1) and the value of square of spontaneous polarization (Ps2) linearly increased with increasing ω2[A1(1TO)], where a and c are the lattice parameters of a and c-axes. This indicates that monitoring A1(1TO) mode is efficient as a characterization method of ferroelectricity. It can also be used as a novel nondestructive process check or reliability assessment technique during fabrication of microelectromechanical systems (MEMS) using piezoelectric materials.

This paper reports on the defect structures formed upon strain relaxation in pulsed laser-deposited complex oxide superlattices consisting of the ferromagnetic metal, La0.67Sr0.33MnO3, and the antiferromagnetic insulator, La0.67Sr0.33FeO3. Atomic resolution scanning transmission electron microscopy and electron energy loss spectroscopy were used to characterize the structure and chemistry of the defects. For thinner superlattices, strain relaxation occurs through the formation of 2-D stacking faults, whereas for thicker superlattices, the prolonged thermal exposure during film growth leads to the formation of nanoflowers and cracks/pinholes to reduce the overall strain energy.

Hydrothermal approach is widely used for the synthesis of zinc oxide (ZnO) nanowires. Zinc nitrate hexahydrate, zinc acetate and zinc chloride are three common salts that are used for synthesis. Among these, zinc nitrate hexahydrate is primarily used in many studies and zinc chloride is preferred for electrodeposition. In this work, zinc acetate dihydrate salt is used for the growth of ZnO nanowires and the effects of time, temperature, solution concentration and concentration ratios of the precursor chemicals are investigated. It is found that the growth time and solution concentration control the lengths of the nanowires, whereas the precursor concentration ratio and solution concentration control their diameter. High solution concentrations and high zinc acetate dihydrate concentrations lead to the development of thin film morphology. Optimum growth parameters are obtained and suggested for the use of zinc acetate dihydrate as a zinc source for growing ZnO nanowires with high aspect ratio (AR). The use of zinc acetate dihydrate leads to the formation of ZnO nanowires without impurities and eliminates the need for using extra capping agents.

Low temperature (25 °C–80 °C) synthesis of zinc oxide (ZnO) nanoparticles (<20 nm) at short synthesis periods (∼30 min) was achieved by precipitation. The precipitation system was formed using zinc acetate dihydrate as zinc source, ethylene glycol (EG) as solvent and polyvinyl pyrrolidone (PVP) as chelating agent. The size of spherical ZnO nanoparticles was manipulated by the choice of precipitation temperature (13.0 ± 1.9 nm at 25 °C and 9.0 ± 1.3 nm at 80 °C), which essentially changes the nature of adsorption events between ZnO crystals and organic molecules. The particle size can also be regulated by the amount of chelating agent as a result of further enhancement in adsorption between ZnO crystals and organic additives. The spherical ZnO nanoparticles were agglomerated into triangular form when different solvent was used – by substituting water for EG, which has different adsorption ability. Accordingly, formation and growth mechanisms controlling the size and morphology of ZnO nanoparticles have been proposed.

Fabrication of thin film nanocomposites via decomposition and self-assembly from the vapor phase is a promising path for cost-effective fabrication of multifunctional materials. In particular, oxides as a new class of energy materials allow for rich functionalities, e.g., by combining p- and n-doped systems in catalytic or light harvesting units. Combining A-site doped perovskites ABO3 with CoFe2O4 spinel, we have investigated thin film phase composition and nanocomposite morphology in the pseudobinary system La0.6Sr0.4BO3–CoFe2O4 for B = Fe, Co, and Mn. We observe formation of an epitaxial two-phase nanocomposite for B = Fe, i.e., the coexistence of La0.6Sr0.4FeO3 and CoFe2O4. In contrast, for B = Co or Mn nanocomposites are formed, where perovskite La0.6Sr0.4BO3 solid solutions coexists with Co-rich spinel and periclase phases. We derive conclusions for the preparation of perovskite-spinel nanocomposites with well-designed doping levels.

Flowerlike hierarchical Bi2MoO6 and Bi2MoO6:Er3+ microspheres were synthesized by a hydrothermal method. The crystalline size of microspheres decreases with increasing Er3+ concentration. The incorporation of Er3+ has no evident influence on the morphology of Bi2MoO6. The photocatalytic activity of microspheres was evaluated by the degradation of rhodamine B (RhB) aqueous solution under simulated solar light. The best photocatalytic performance was observed when the Er3+ concentration was 0.5%. In addition to the aforementioned high photocatalytic activity, the Bi2MoO6:Er3+ microspheres can emit pure green upconversion (UC) luminescence (2H11/2/4S3/2 → 4I15/2) under 980 nm excitation. We suggest that the enhancement of photocatalytic activity of Bi2MoO6:Er3+(0.5%) is related to the UC luminescence of Er3+ ions. In addition, the BET surface areas of samples increased with increasing Er3+ concentration, which is also benefit for RhB adsorption.

Mechanisms leading to correlation between structural phase transitions in functional oxides and consequent insulator–metal transitions driven by band gap closure are an active area of research. In cases where large volume changes are present, structural stability considerations become important. Here, we present in situ studies of mechanical instability of VO2 grown on self-supported Si3N4 membranes spanning the structural phase transition boundary of vanadium dioxide. We observe film cracking across the phase transition, and the transition-induced cracks correlate with the symmetry change and the corresponding changes in the optical/electrical response arising from the insulator–metal transition. Transmission electron microscopy studies revealed twinned platelets proximal to crack regions. Interestingly, the membranes are mechanically stable until a large fraction of resistance change occurs across the phase transition. The ability to manipulate the stability and controlled rupture of self-supported membranes through temperature or other stimuli could be of interest to microelectromechanical systems and sensor devices.

Intense broad absorption bands centered around 1.7, 2.5, 3.1, and 3.7 eV take place in Er3+-diffused layer formed near MgO (5 mol%)-doped LiNbO3 crystal surface by in-diffusion of Er metal under Li-poor atmosphere. These bands are tentatively attributed to the defect absorption of small polarons, bipolarons, F-centers, and Q-polarons created due to Er3+ in-diffusion and Li2O loss from the crystal. It is interesting that the number, type, area, and peaking position of the bands can be controlled by the diffusion temperature and further oxidation treatment. Such material is a promising medium for data storage based upon two-color holography.

Solid polymer electrolytes (SPEs) with poly(vinylidene fluoride-hexafluoropropylene) [P(VdF-HFP)] as polymer host, doped with magnesium trifluoromethanesulfonate (MgTf) and 1-butyl-3-methylimidazolium trifluoromethanesulfonate (BMIMTf) have been synthesized via solution casting method. This P(VdF-HFP)/MgTf/BMIMTf-based SPE achieves ∼3 × 10−3 and ∼7 × 10−3 S·cm−1 at 30 and 80 °C, respectively, with 75 part by weight (pbw) of BMIMTf. At the same time, they are also examined by means of frequency-dependent conductivity, dielectric permittivity, and dielectric modulus studies. Scanning electron microscopy reveals drastic morphological changes on SPE with small amount of BMIMTf. Even though it gradually changes back to its undoped state with higher concentration, it appears to be swollen. Examination on relationship between ionic conductivity and crystallinity by differential scanning calorimetry technique shows inconsistency at concentration higher than 75 pbw. This observation is related to greater ion–ion interaction due to excessive BMIMTf. Photoluminescence is also used to detect structural alterations in the local environment of SPE.

This study investigated the performance of membrane electrode assembly (MEA) fabricated with various loadings of platinum catalyst on carbon nanotubes (CNTs) and sulfonated membrane at constant conditions of duration, temperature and pressure. The fabricated MEA was tested in a single proton exchange membrane (PEM) fuel cell unit using hydrogen and oxygen as fuel and oxidant gases respectively. The results obtained show that the performance of the MEA in the cell improves with increase in loading of the catalyst on the electrodes. The results obtained on kinetics of the fuel cell indicate that the MEA samples fabricated with 30 and 40 wt% Pt catalyst electrodes conform to the Tafel equation whereas the remaining MEA fabricated with 10 and 20 wt% catalyst samples do not obey the Tafel equation due to large values of their overpotential. Hirschenhofer and Tafel equations were used to model the performance of the catalyst electrodes in the cell and the simulated voltage obtained from the former showed better conformity with the experimental voltage than the latter.

Supercritical fluid (SCF) N2 was used as a physical foaming agent to fabricate microcellular injection-molded poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV)–poly(butylene adipate-co-terephthalate) (PBAT)–hyperbranched-polymer (HBP)–nanoclay (NC) bionanocomposites. The effects of incorporating HBP and NC on the morphological, mechanical, and thermal properties of both solid and microcellular PHBV–PBAT blends were studied. NC exhibited intercalated structures in solid components, but showed a mixture of exfoliated and intercalated structures in the corresponding microcellular nanocomposites. The addition of NC improved the thermal stability of the resulting nanocomposites. The addition of HBP and NC reduced the cell size and increased the cell density of microcellular components. The addition of HBP and NC enhanced the degree of crystallinity for both solid and microcellular components. Moreover, with the addition of HBP, the area under tan δ curve, specific fracture toughness, and strain-at-break of the PHBV-based nanocomposite increased significantly whereas the storage modulus, specific Young’s modulus, and specific tensile strength decreased.

To improve the thermoelectric properties of LaCeFe3CoSb12 skutterudite materials, the LaCeFe3CoSb12 nanopowders of disordered structure were fabricated through a laser melting and quenching process and then were hot pressed into bulk pellets with the coexistence of ordered and disordered structures by mixing the disordered powders with the raw LaCeFe3CoSb12 crystalline materials. The results suggest that the introduced disordered structure can increase Seebeck coefficient from 57 to 179 μV/K while reduce thermal conductivity from 3.1 to 1.5 W/(m·K), although electrical conductivity can be decreased from 98,000 to 43,000 S/m, and consequently, figure of merit can be enhanced from 0.11 to 0.90 at 773 K. Therefore, fabricating a material with the coexistence of disordered and ordered structures can be considered as an effective way to obtain a high figure of merit, and this strategy can be also applied to other thermoelectric alloys.

A facile method to control the morphology of FeNi3 nanoparticles by solution reduction reaction is presented. The spherical to platelet FeNi3 particles were obtained by changing pH from 11.5 to12.5 with 0.16 mol/L of hydrazine under ultrasound irradiation, with the ratio of Fe2+ to Ni2+ as 1:3. The amount of hydrazine had little influence on the morphology of the particles. The saturation magnetization (Ms) and coercive force (Hc) of the platelet particles were 59 emu/g and 120 Oe, respectively. The real part μ′ of the permeability of the platelet particles was about 2.43–2.71 and was frequency-independent in the range of 0.1–1.0 GHz. The imaginary part (μ′′) of the particles showed increase from 0.04 to 2.14 within the same frequency range.

Ni3N was prepared by gaseous nitriding of nickel substrates using gas mixtures of high nitrogen activities, composed of NH3 and H2 at 1 atm and at temperatures between 175 °C and 550 °C. At least above 300 °C closed Ni3N layers developed, which possess distinct compressive macrostrain parallel to the surface. The observed hkl-anisotropy of the macrostrain could be ascribed to the elastic anisotropy as indicated by the single-crystal elastic constants of Ni3N obtained from first-principles calculations performed in this work. The macrostress originates from the thermal misfit between layer and substrate, developing upon cooling. The extent of macrostress is reduced by partial misfit accommodation by plastic deformation as well as by porosity.