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Epitaxial BaSnO3 (BSO) thin films doped with different rare-earth elements (La, Pr, and Nd) were prepared by a simple solution deposition method. Grain size engineering through processing was achieved to tune both lateral and vertical grain sizes, resulting in obvious increments in carrier mobility. Improved performance with the room-temperature mobility exceeding 35 cm2 V−1 s−1 and resistivity as low as 0.55 mΩ cm was realized. The results will open a low-cost route for preparation of large-area BSO thin films with improved optoelectronic properties through the solution method. [ABSTRACT FROM AUTHOR]

We investigate the effect of Jahn-Teller (JT) active Cu2+ ions on the structural, magnetic, and ferroelectric properties of Co1–xCuxCr2O4 (0 ≤ x ≤ 0.4). All the samples can be indexed with a cubic lattice with space group Fd 3 ¯ m at room temperature. All the samples undergo a paramagnetic-ferrimagnetic transition at TC and spiral ferrimagnetic ordering at TS. The magnetization measurements manifest that magnetization reversal occurs in the x = 0.2 and 0.3 samples. The x = 0.3 sample possesses a rather large polarization of 14 μC/m2, which is 7 times in magnitude compared with the CoCr2O4 single crystal. The analysis of the infrared active phonon modes implies that two T 1 u (IR) optical phonon modes are gradually split into a doublet at around 40 K, implying the lowering of lattice symmetry. The presence of a low-symmetry tetragonal phase becomes polar and enhances the electric polarization of Co0.7Cu0.3Cr2O4. [ABSTRACT FROM AUTHOR]

Developing lead-free film dielectric capacitors with high-performance of energy storage density, efficiency, fatigue endurance, and thermal stabilities is desirable. Here, we report energy storage properties in (1-x)BaTiO3-xBi3.25La0.75Ti3O12 thin films. It is revealed that a 0.6BaTiO3-0.4Bi3.25La0.75Ti3O12 thin film with a thickness of 280 nm and a crystallization temperature of 650 °C shows a breakdown strength of 3.23 MV/cm with a large polarization value and dielectric constant. An ultrahigh energy storage density of 61.1 J/cm3 and an efficiency of 84.2% are simultaneously achieved at room temperature. Additionally, excellent fatigue endurance after 6 × 109 cycles and good thermal stability up to 150 °C are observed, implying excellent energy storage performance in 0.6BaTiO3-0.4Bi3.25La0.75Ti3O12 thin films. [ABSTRACT FROM AUTHOR]

Thin film ferroelectric capacitors (TFFCs) with excellent energy storage have attracted increasing attention due to the electronic devices toward miniaturization and integration. BiFeO3 (BF)/ Bi3.25La0.75Ti3O12 (BL) based thin films are prepared by chemical solution deposition for energy storage. Ultrahigh energy storage with a recoverable energy density Ure of 54.9 J/cm3 and an efficiency g of 74.4% is observed in the bilayered BF/BL thin films. Further improvement of energy storage is realized in trilayered BL/BF/BL thin films with a Ure of 65.5 J/cm3 and an efficiency g of 74.2% at an electric field of 2753 kV/cm as well as excellent fatigue endurance up to 109 cycles. The results suggest that BF/BL based thin films can be used as lead-free TFFCs in energy storage applications. [ABSTRACT FROM AUTHOR]

Environmentally benign Bi3.25La0.75Ti3O12 (BLTO) thin film capacitors were prepared by a cost effective chemical solution deposition method for high energy density storage device applications. Low annealing temperature annealed BLTO thin films showed very slim hysteresis loops with high maximum and small remnant polarization values. Increasing the applied electric field to 2040 kV/ cm, the optimized BLTO thin films show a high recoverable energy density of 44.7 J/cm3 and an energy efficiency of 78.4% at room temperature. Additionally, the BLTO thin film capacitors exhibited excellent fatigue endurance after 4x108 cycles and a good thermal stability up to 140°C, proving their strong potential for high energy density storage and conversion applications. [ABSTRACT FROM AUTHOR]

(1-x)(0.94Bi0.5Na0.5TiO3-0.06BaTiO3)-xBiFeO3 (0 ≤ x ≤0.9) ternary ceramics were prepared by the modified Pechini method. X ray diffraction patterns manifest that the samples undergo a gradual structural transformation from the rhombohedral-tetragonal morphotropic phase boundary to the rhombohedral phase with the increasing content of BiFeO3. Room temperature ferromagnetism was observed in BiFeO3-rich samples with x ≥ 0.6, and this ferromagnetism can be ascribed to the suppression of the spiral spin structure with the canting of antiferromagnetically ordered spins. The BiFeO3-rich samples (x=0.6-0.8) exhibit superior ferroelectric properties with the maximum remanent polarization of 44.7 lC/cm², as confirmed by the positive-up negative-down measurement to exclude the contribution of leakage current. The coexistence of room-temperature ferromagnetism and ferroelectricity manifests that the lead-free BiFeO3-based solid solutions are quite promising multiferroic materials and may be important for potential applications in BFO-based magnetoelectric devices. [ABSTRACT FROM AUTHOR]

We investigate the effect of high magnetic-field annealing on the microstructural, ferroelectric, and magnetic properties of Bi6Fe1.4Co0.6Ti3O18 thin films. The magnetic field can lower the energy barrier for nucleation and improve the grain connectivity. The application of magnetic field of 6T parallel to the film plane can substantially enhance the remnant polarization Pr from 18.1 to 29 μC/cm² as a result of the variation in grain size and growth orientation caused by magnetic field annealing. Moreover, the remnant magnetization Mr is substantially improved from 2.48 to 4.56 emu/cm³ arising from the enhanced exchange coupling due to the better grain connectivity. These results demonstrate that high magnetic-field annealing is an effective way to optimize multiferroic properties of the Aurivillius compounds. [ABSTRACT FROM AUTHOR]

As a type of perovskite transparent conducting oxides, La-doped BaSnO3 is considered as a very important material to construct all transparent perovskite devices. The difficulty in achievement of large-area films with high electrical mobility has hindered the development of La-doped BaSnO3 films. Here, we report the results about chemical solution deposition of Ba0.92La0.08SnO3-δ (BLSO) films. The post-annealing and atmosphere as well as lattice mismatch have been investigated. Post-annealing at 1000 °C can obviously improve the performance due to the enhanced crystallization. Under post-annealing in N2 atmosphere the room-temperature resistivity and electrical mobility can achieve 3.25 mΩ cm and 11.09 cm² V-1 s-1, respectively, for the BLSO on LaAlO3 single crystal substrates due to the enhanced oxygen deficiencies. BLSO films with different orientation can be easily obtained by selection of the substrates, showing isotropic physical properties. Furthermore, the room-temperature resistivity and mobility are optimized to 1.8 mΩ cm and 23.04 cm² V-1 s-1 when SrTiO3 single crystal substrates with smaller lattice mismatch are used due to the decreased dislocation density. The results will provide an alternative route to fabricate large-area transparent conducting alkaline-earth stannate films with high performance using low-cost chemical solution deposition. [ABSTRACT FROM AUTHOR]

The thermoelectric properties of MoS2 armchair nanoribbons with different width are studied by using first-principles calculations and Boltzmann transport theory, where the relaxation time is predicted from deformation potential theory. Due to the dangling bonds at the armchair edge, there is obvious structure reconstruction of the nanoribbons which plays an important role in governing the electronic and transport properties. The investigated armchair nanoribbons are found to be semiconducting with indirect gaps, which exhibit interesting width-dependent oscillation behavior. The smaller gap of nanoribbon with width N = 4 (Here, N represents the number of dimer lines or zigzag chains across the ribbon width) leads to a much larger electrical conductivity at 300 K, which outweighs the relatively larger electronic thermal conductivity when compared with those of N = 5, 6. As a result, the ZT values can be optimized to 3.4 (p-type) and 2.5 (n-type) at room temperature, which significantly exceed the performance of most laboratory results reported in the literature. [ABSTRACT FROM AUTHOR]

Electrical transport properties of La2/3Sr1/3VO3 (LSVO) thin films grown on LaAlO3 (LAO) and SrTiO3 (STO) substrates have been investigated. It is found that the LSVO/LAO show metal-insulator transition when decreasing the temperature, while the LSVO/STO exhibit metallic behavior. The difference in transport properties of LSVO thin films has been discussed based on the variation of oxygen content and can be attributed to different oxygen substrate-to-film transfer. These results highlight the crucial role of oxygen stoichiometry in determining the physical properties of LSVO and the importance of oxygen-substrate contribution in LSVO thin films. [ABSTRACT FROM AUTHOR]

We have demonstrated the effect of gradients in phase composition and microstructure of p-type CeFe4Sb12 melt-spun ribbons on Seebeck coefficient by using a thermoelectric (TE) screening tool in conjunction with x-ray diffraction. The spatial Seebeck coefficient variation was found to correlate with the changes in the phase composition and microstructure. The observed gradient was the result of a postannealing effect caused by the thermal lag between the contact surface with the roller and the free surface. Our results illustrate the application of our screening tool to the three-dimensional variation in Seebeck coefficient in a model TE material. [ABSTRACT FROM AUTHOR]

Giant exchange bias with a shift up to 3.86 kOe has been observed in γ-Fe2MnGa alloy in which a ferromagnetic to antiferromagnetic transition takes place at 250 K. The transition can be suppressed to lower temperatures by higher magnetic fields at a shift rate of 10.3 K/kOe. Exchange bias and enhanced coercivity occur simultaneously, revealing an exchange coupling between the coexisting antiferromagnetic and ferromagnetic phases. Meanwhile, the internal exchange coupling inside the antiferromagnetic clusters dynamically ensures their unidirectional anisotropy during their size changing following the external magnetic field. [ABSTRACT FROM AUTHOR]

The electronic properties of (Sb0.75Bi0.25)2Te3 compound are examined by using the full-potential linearized augmented plane-wave method. The transport coefficients are then calculated within the semiclassical Boltzmann theory, and further evaluated as a function of chemical potential assuming a rigid band picture and constant relaxation time. The ZT value is thus estimated by inserting an averaged thermal conductivity. Our theoretical calculations give a valuable insight on how to enhance the thermoelectric performance of this compound, and many potential doping elements and their optimal concentrations are suggested. [ABSTRACT FROM AUTHOR]

Physical and electrical properties of PtSi nanowires (NWs) fabricated on a silicon-on-insulator wafer are investigated. The Si consumption rule in NW silicidation is consistent with that of planar process. The cross-sectional area ratio between PtSi NW and Si NW is about 1.5:1. An electrical method is used to evaluate the silicidation degree of NWs. According to the dependence of the current passing through the NW on the backside substrate voltage, we can determine whether the Si NW is fully or partially silicided. The electrical evaluation results are in agreement with transmission electron microscopy inspections. [ABSTRACT FROM AUTHOR]

Ba(Zr0.2Ti0.8)O3 (BZT) thin films on Pt(111)/Ti/SiO2/Si(100) substrates without and with CaRuO3 (CRO) buffer layer were fabricated at 650 °C in situ by pulsed laser deposition. The BZT thin films showed a dense morphology, many clusters are found on the surface images of BZT/Pt films, which are composed by nanosized grains of 25–35 nm; the average grain size of BZT/CRO films is about 80 nm, which lager than that of BZT/Pt thin film. The dielectric constants and dissipation factors of BZT/Pt and BZT/CRO thin films were 392 and 0.019 and 479 and 0.021 at 1 MHz, respectively. The dielectric constant of BZT/Pt and BZT/CRO thin films changes significantly with applied dc bias field and has high tunabilities and figures of merit of ∼70% and 37 and 75% and 36, respectively, under an applied field of 400 kV/cm. The possible microstructural background responsible for the high dielectric constant and tunability was discussed. [ABSTRACT FROM AUTHOR]

Dielectric response and electrical conduction properties of 0.94Pb(Fe1/2Nb1/2)O3–0.06PbTiO3 single crystals grown by the Bridgman method were studied. It was found that the single crystals did not show any sign of the presence of Curie temperature between room temperature and 300 °C. However, they exhibited very high dielectric constant at a frequency lower than 100 kHz, in the order of 105. Relaxation occurred at higher frequencies with a large decrease in dielectric constant, to about 1500. The thermal activation energy for relaxation was found to be ∼0.17 eV, which is quite close to that for ac conductivity. It followed that the relaxation was attributed to the carriers hopping conduction, which is related to the possible jump motion of additional 3d electron between the equivalent positions of Fe ions. [ABSTRACT FROM AUTHOR]

We have performed a study on the dielectric properties of (Ba0.90Ca0.10)(Ti0.75Zr0.25)O3 bulk ceramics prepared by a sol–gel technique in the cooling temperature range from 400 to 213 K. The ceramics are found to exhibit an interesting dielectric response under the presence of a dc bias field. The field dependence of dielectric constant is stronger at T≈Tm (Tm is the temperature of dielectric maximum) and the field-induced variation of dielectric constant Δε is nonzero for T-Tm<150 K. One striking feature of these ceramics is that they possess a broad optimum value of figure of merit (as high as 200 at 30 kV/cm) between the temperature range from 295 and 330 K. At room temperature, the high tunability (K=60%), low-loss tangent (≈0.003), and large figure of merit (200), clearly indicate that these ceramics are suitable candidates for microwave applications. [ABSTRACT FROM AUTHOR]