Structural and electrochemical properties of spray deposited molybdenum trioxide (α-MoO3) thin films

Journal of Solid State Electrochemistry - Nanostructured molybdenum trioxide (α-MoO3) thin films were deposited to investigate effect of substrate temperature on microstructural,...     

Structure,chemical stability and electrical properties of BaCe0.9Y0.1O3−δ modified with V2O5

Wet vacuum impregnation method was applied in order to evaluate the possibility of the formation of the material in BaCe_0.9Y_0.1O_3?δ–V₂O₅ system. Single-phase BaCe_0.9Y_0.1O_3?δ samples, synthesised by solid-state reaction method, were impregnated with the solution of vanadium(V) oxide precursor. Multi-step, multi-cycle impregnation procedure was applied to enhance the impregnation efficiency. Partial decomposition of Y-doped BaCeO₃ in contact with the solution of the precursor, resulting in the formation of vanadium containing phases (CeVO₄ and BaV₂O₆) on the materials surface, was observed. However, the presence of vanadium was also confirmed for the inner parts of the materials. The synthesised materials were submitted for exposition test to evaluate their chemical stability towards CO₂/H₂O. All BaCe_0.9Y_0.1O₃-based materials modified by impregnation revealed higher chemical stability in comparison with single-phase un-modified BaCe_0.9Y_0.1O_3?δ, since the amount of barium carbonate formed during the exposition was significantly lower. The total electrical conductivity of the received multi-phase materials was generally slightly lower than for the reference BaCe_0.9Y_0.1O_3?δ sample, since the presence of the additional phases had a blocking effect on materials conductivity. The values of BaCeO₃ lattice parameters and the Seebeck coefficient did not show the modification of the defects structure of Y-doped BaCeO₃ during applied synthesis procedure.

     

Structural,electrical and optical properties of Lin@C20 (n = 1–6) nanoclusters

The current research was undertaken to investigate the structural, electrical, and optical properties of C₂₀ fullerene decorated with different numbers of lithium (Li) atoms on its surface. The stability of the structure increased as the number of lithium atoms increased. Increasing the number of lithium atoms around C₂₀ from one to four slightly increased the E_g (energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital). Increasing the number to five or six narrowed the E_g. The electrical properties such as ionization potential (I), electron affinity (A), chemical potential (μ), global hardness (η), global softness (γ), global electrophilicity (ω), and electronegativity (χ) were also calculated. The polarizability (α) and first hyperpolarizability (β₀), which correspond to the linear optical and nonlinear optical properties, respectively, were also calculated. An intense increase in β₀ was recorded as the effect of five Li atoms adsorbed onto the C₂₀ surface. The results of this study can be used to design and fabricate nanomaterials with adjustable electro-optical properties.     

Effect of Tb content on microstructure and ferroelectric properties of Bi4−x Tb x Ti3O12 thin films grown by sol–gel method

The effects of Tb substitution on the structural and electrical properties of ferroelectric Bi₄Ti₃O₁₂ (BTO) thin films grown on Pt/TiO₂/SiO₂/Si substrates by a sol–gel process have been reported. X-ray diffraction indicated A-site Tb substitutions did not change the polycrystalline bi-layered Aurivillius structure of the BTO, but a lattice distortion was observed. The leakage current behavior at room temperature of the films was studied and it was found that the leakage current density decreased from 10^?2 to 10^?4 A/cm² with the increase of x under 150 kV/cm. The remnant polarization (2P _r ) and dielectric constant (ε _r) increase firstly and then decreases with the increase of the Tb content. We observed a substantial increase in the remnant polarization (2P _r ) with Tb substitution and obtained a maximum value of~60 μC/cm² at an applied electric field of 500 kV/cm for x = 0.4. Moreover, this BTT-0.4 capacitor did not show fatigue behaviors after 1.0 × 10¹⁰ switching cycles, suggesting an anti-fatigue character.     

Luminescence and dielectric properties of c-axis oriented (Bi1.90Eu0.10)(V1−zMoz)O5.5 ferroelectric thin films

(Bi_1.90Eu_0.10)(V_1−zMo_z)O_5.5 (z = 0, 0.05, 0.10, 0.15 and 0.20) thin films with c-axis oriented were prepared on Pt(111)/Ti/SiO₂/Si substrates by using chemical solution deposition method. The effect of Mo⁶⁺ concentration on the structure, luminescence properties and dielectric properties of the thin films were characterized systematically. X-ray diffraction data indicates that the thin films with low Mo⁶⁺-doping content can remain Bi₂VO_5.5 structure. When the Mo⁶⁺-doping content z reaches to 0.15, the thin films are a mixture of diphase with the main phase Bi₂VO_5.5 and secondary phase Bi₂MoO₆. Under UV irradiation, all the thin films emit a bright red or orange emission which origin from Eu³⁺. With increasing Mo⁶⁺-doping content z, the relative intensity of the Red and Orange emissions show obviously change. The value of Red/Orange ratio first decrease, and it reached minimum when z is 0.15, then it recover to the initial value. The variation trend of the Red/Orange ratio reflects the change of the lattice symmetry. Dielectric constant of the thin films increased with the increasing of the Mo⁶⁺ concentration while dielectric loss decreased. The decrease of the quantities of oxygen vacancies and the generation of Bi₂MoO₆ phase are responsible for the improvement of electric properties. These results explain that Eu³⁺ion can be used as an effective luminescent probe in (Bi_1.90Eu_0.10)(V_1−zMo_z)O_5.5 (z = 0, 0.05, 0.10, 0.15 and 0.20) thin films, and the electric properties of the thin films can be improved by Mo⁶⁺ doping.     

四元Mg0.9Ti0.1Ni0.9X0.1(X=Mn,Zn,Co,Fe)系列合金的制备及性能研究

用机械合金化法合成了Mg0·9Ti0·1Ni0·9X0·1(X=Mn,Zn,Co,Fe)系列合金.X射线衍射(XRD)结构分析表明,用X部分替代Ni后,促进了Mg0·9Ti0·1Ni合金的非晶化过程.用Co和Fe部分替代Ni提高了合金的放电容量,但却降低了合金的循环稳定性.用Zn和Mn部分替代Ni提高了合金电极的循环寿命,尤其是Mg0·9Ti0·1Ni0·9Zn0·1合金电极经10个充放电循环后,其放电容量仍可达到313·8mA·h/g.对添加Co后的合金进行p-c-T测试发现,Mg0·9Ti0·1Ni0·9Co0·1合金的吸放氢容量明显比Mg0·9Ti0·1Ni合金高,这与电化学所测到的结果一致.     

Synthesis, electrical and thermal properties of Bi4V2−xMexO11 (x = 0.0 and 0.02) ceramics

Polycrystalline ceramic samples of Bi₄V_2?xMe_xO₁₁ (Me = Nb, Zr, Y and Cu and x = 0.0 and 0.02) have been synthesized by standard solid state reaction method using high purity oxides. The formation of the compounds have been analysed by X-ray diffraction method. The dielectric constant, dielectric loss and AC conductivity as a function of frequency and temperature have been measured. The dielectric studies indicate that the material is highly lossy and hence its AC conductivity increases with the increase of temperature. The DC conductivity of material has been measured as a function of temperature from room temperature to 380 °C and its activation energy was calculated using the relation σ = σ ₀exp (?E _a/kT). The modulated differential scanning calorimetry has been used to investigate the effect of substitution on the heat capacity and heat flow of the compounds. The results are discussed in detail.     

The (100) orientation evolution and temperature-dependent electrical properties of Bi(Zn1/2Ti1/2)O3–PbTiO3 ferroelectric films

The 0.2Bi(Zn_1/2Ti_1/2)O₃–0.8PbTiO₃ (0.2BZT–0.8PT) ferroelectric thin film was successfully fabricated on Pt(111)/Ti/SiO₂/Si substrates by a sol–gel method. The result indicates that the film exhibits the (100) preferred orientation and has a relatively dense and uniform microstructure with a thickness of ~230 nm. The formation mechanism of the oriented films was ascribed to the growth of the (100) oriented PbO layer at ~450 °C during a layer-by-layer crystallization process. Temperature-dependent electrical properties of the 0.2BZT–0.8PT films were investigated, showing that the film has a potential for high temperature applications.     

Synthesis and structural properties of (Y,Sr)(Ti,Fe, Nb)O3−δ perovskite nanoparticles fabricated by modified polymer precursor method

The yttrium, iron and niobium doped-SrTiO₃ powders have been successfully fabricated by a modified low–temperature synthesis method from a polymer complex. The usage of strontium hydroxide precursor instead of conventional strontium nitrate or strontium carbonate provides to the possibility of significant decrease of annealing temperature. It allows to prepare a material with sphere-shape grains of nanometric size (15–70 nm). The results of thermal analysis indicate that the crystallization of precursor takes place at different stages. The product after heat treatment at 600 °C for 3 h in air was also characterized by X-Ray diffraction method (XRD) and Fourier transform – infrared spectroscopy (FT-IR). After the crystallization and the impurity removal process, a single-phase material was obtained in case of all analyzed samples. The morphology of obtained nano-powders was also studied by a scanning electron microscopy (SEM). It can be concluded, that this method allows obtaining a perovskite phase of a metal doped SrTiO₃ with nanometric particles.     

Single Crystal Studies of Ternary Transition-Metal Molybdenum Selenides MMo6Se8 (M = Ti, Fe, Mn, Cr and Co)

Magnetic properties have been measured in single crystals of selenium-based Chevrel-type M _xMo₆Se₈, with M = Ti, Fe, Mn, Cr and Co, in which x(M) is equal to unity, except for Ti (x ~ 0.9) and Co (x ~ 0.5). Presence of impurities, such as the binary Mo₃Se₄ sub-product, is absolutely excluded and reported results are representative of the intrinsic properties of the reported compounds. For polycrystalline ScMo₆Se₈ and single crystals of Ti_0.88Mo₆Se₈, the Pauli-like temperature-independent magnetic susceptibility allows having a good estimation of the non-magnetic contribution of the Mo₆Se₈ sublattice. Crystal field effects were seen for polycrystalline VMo₆Se₈. Spectacular results were obtained for FeMo₆Se₈ (canted antiferromagnetic compound with high magnetic anisotropy), CrMo₆Se₈ (antiferromagnetism, T_N = 12 K), MnMo₆Se₈ (metamagnetic compound) while the properties of Co_0.54Mo₆Se₈ can be interpreted by magnetic exchange interactions J_AF ~ 100 K. These results are discussed in connection with structural properties and transport measurements obtained in single crystal specimens.     

Synthesis,electrical and thermal properties of Bi4V2−xMexO11 (Me=Nb,Zr, Y and Cu with x = 0.0 and 0.06) ceramics

Polycrystalline ceramic samples of Bi₄V_2?xMe_xO₁₁ (Me=Nb, Zr, Y and Cu and x = 0.0 and 0.06) have been synthesized by standard solid state reaction method using high purity oxides. The formation of the compounds have been analysed by X-ray diffraction method. The dielectric constant, dielectric loss and AC conductivity as a function of frequency and temperature have been measured. The dielectric studies indicate that the material is highly lossy, and hence, its AC conductivity increases with the increase of temperature. The DC conductivity of material has been measured as a function of temperature from room temperature to 723 K and its activation energy was calculated using the relation σ = σ ₀exp (?E _a/kT). The modulated differential scanning calorimetry has been used to investigate the effect of substitution on the phase transition (heat capacity and heat flow) of the compounds. The results are discussed in detail.     

Effect of chemical composition and heat treatment condition on microstructure and magnetic properties of nanocrystalline BaDyxFe12−xO19 (x = 0.1, 0.2, 0.3, 0.4) microfibres

A series of BaDy_xFe_12?xO₁₉ ferrite microfibres have been synthesized from metal nitrates and citric acid by the sol–gel method. TG-DSC, XRD, FTIR, FESEM, TEM and VSM were employed to characterize the thermal decomposition process, crystallite sizes, structure and magnetic properties of ferrite microfibres. The effect of calcined temperature, holding time, ion substitution on structure, magnetic properties of barium ferrite microfibres was investigated. The nanoparticle growth mechanism of ferrite microfibres was discussed. The results indicated that the hexaferrite phase was formed at 750 °C and Dy³⁺ ions entered the magnetoplumbite lattice. However, the reflections shift to a lower angle and the characteristic peaks of ferrite microfibres in FTIR shift to the lower wavenumber with the Dy content increasing. The VSM results shown that saturation magnetization (M _s ) gradually increased with calcined temperature increasing and holding time prolonging, while coercive force (H _c ) revealed an increase at first and then decreases. With the Dy content increasing, the M _s achieved values of M _s  = 50 emu?g^?1 (297 K) and 70 emu?g^?1 (77 K) and the H _c value shown a continuous reduction from 515 kA??m^?1 (297 K) and 435 kA?m^?1 (77 K) (x = 0.0) to 242 and 215 kA?m^?1 (x = 0.4).     

Dielectric,pyroelectric and piezoelectric properties in the (1 − x)(0.1BaTiO3–0.9NaNbO3)–xLiNbO3 system

New lead free piezoceramics with the given compositions (1 − x)(0.1BaTiO₃–0.9NaNbO₃)–xLiNbO₃(0.01 ≤ x ≤ 0.125) were prepared by solid–state reaction technique. XRD patterns revealed a single perovskite-structured phase only for 0.01 ≤ x < 0.05. The dielectric, pyroelectric and piezoelectric responses were investigated for compositions with x = 0.01 and 0.02. For both compositions, ɛ’_r exhibited a sharp peak with no frequency dependence (classical ferroelectrics). Losses displayed a strong dispersion at low frequencies in the paraelectric phase which was attributed to Li ionic conductivity in these compositions. The spontaneous polarization was found to be 35 and ≈22 μC cm⁻² for x = 0.01 and 0.02 respectively. The transverse piezoelectric coefficient d₃₁ measured for x = 0.01 reached value of 37 pC/N at room temperature while the planar coupling factor was about 0.23.     

Structural and magnetic properties of homoleptic iron(III) complexes containing N-(8-quinolyl)-salicylaldimine [Fe(Qsal)2]+X− {X = I or (Qsal)FeCl3}

The structural properties of two homoleptic iron(III) complexes containing N-(8-quinolyl)-salicylaldimine (qsalH) are reported on the basis of two single-crystal X-ray diffraction experiments. The complexes are shown to share the general formula [Fe(qsal)₂]⁺X^? {X = I (1) or (qsal)FeCl₃ (2)} and include one new complex 2 and one previously reported complex 1 for which structural details were until now unknown. Variable-temperature magnetic susceptibility measurements on both samples indicate the nature of the spin state of the metal ion, which is low-spin for 1 and high-spin for 2. Mössbauer spectra are recorded for 1 at 293 and 5.6 K and indicate unusual temperature-dependent behaviour, which corroborates an earlier report.