Improved thermoelectric properties by adding Al for Zn in (ZnO)mIn2O3

The grain size and density of the sintered (Zn_1 − xAl_xO)_mIn₂O₃ bodies decreased with the small Al₂O₃ content (≤ 0.012), and then increased gradually by further increasing the Al₂O₃ content. The addition of Al for Zn in the (ZnO)_mIn₂O₃ led to an increase in both the electrical conductivity and the absolute value of the Seebeck coefficient. This indicates that the power factor was significantly enhanced by adding Al for Zn. The thermoelectric power factor was maximized to 1.67 × 10^− 3 W m^− 1 K^− 2 at 1073 K for the (Zn_0.992Al_0.008O)_mIn₂O₃ sample.     

Enhanced thermoelectric properties of NaCo2O4 by adding ZnO

The primary phase present in the as-sintered Na(Co_1 − xZn_x)₂O₄ (0 ≤ x ≤ 0.1) bodies was the solid solution of the constituent oxides with a bronze-type layered structure. The electrical conductivity of the Na(Co_1 − xZn_x)₂O₄ samples significantly increased with an increase in ZnO content. The sign of the Seebeck coefficient for all samples was positive over the whole temperature range (723-1073 K), i.e., p-type conduction. The power factor of Na(Co_0.95Zn_0.05)₂O₄ showed an outstanding power factor (1.7 × 10^− 3Wm^− 1 K^− 2) at 1073 K. The power factor was above four times superior to that of ZnO-free NaCo₂O₄ (0.4 × 10^− 3Wm^− 1 K^− 2). This originates from an unusually large Seebeck coefficient (415 μVK^− 1) accompanied with high conductivity (127Ω^− 1 cm^− 1) at 1073 K.     

Cadmium oxide, indium oxide and cadmium indate thin films obtained by the sol-gel technique

Thin films of the mixed CdO-In₂O₃ system were deposited on glass substrates by the sol-gel technique. The precursor solution was obtained starting from the mixture of two precursor solutions of CdO and In₂O₃ prepared separately at room temperature. The In atomic concentration percentages (X) in the precursor solution with respect to Cd (1 − X), were: 0, 16, 33, 50, 67, 84 and 100. The films were sintered at two different sintering temperatures (Ts) 450 and 550 °C, and after that, annealed in a 96:4 N₂/H₂ gas mixture at 350 °C. X-ray diffraction patterns showed three types of films, excluding those constituted only of CdO and In₂O₃ crystals: i) For X ≤ 50 at.%, the films were constituted of CdO + CdIn₂O₄ crystals, ii) For X = 67 at.%, the films were only formed of CdIn₂O₄ crystals and iii) For X = 84 at.% the films were constituted of In₂O₃ + CdIn₂O₄ crystals. In all films in the 0 < X < 100 range, the formation CdIn₂O₄ crystals of this material was prioritized with respect to the formation of CdO and In₂O₃ materials. All films showed high optical transmission and an increase of the direct band gap value from 2.4 (for CdO) to 3.6 eV (for In₂O₃), as the X value increases. The resistivity values obtained were in the interval of 8 × 10^− 4 Ω cm to 10⁶ Ω cm. The CdIn₂O₄ films had a resistivity value of 8 × 10^− 3 Ω cm and a band gap value of 3.3 eV.     

Preparation and properties of Ti/SnO2-Sb2O5 electrodes by electrodeposition

Sb and Sn coatings were deposited on Ti substrate by the method of cathode deposition, and the Ti/SnO₂-Sb₂O₅ electrodes were obtained by annealing at different temperatures for 3 h. Ti/SnO₂-Sb₂O₅ coating was characterized using technique such as X-ray diffraction (XRD), and scanning electron microscopy (SEM). Ti/SnO₂-Sb₂O₅ electrode calcined at 550 °C exhibits the best catalytic capacity. Ti/SnO₂-Sb₂O₅ electrode obtained by electrodeposition had longer service life and faster degradation capacity compared with that obtained by dip-coating. Accelerated service life tests were carried out in 0.5 mol L^− 1 H₂SO₄ solution with the current density of 100 mA cm^− 2. Service life of Ti/SnO₂-Sb₂O₅ electrode prepared in present study was 15 h, and it was only 0.14 h for Ti/SnO₂-Sb₂O₅ electrode obtained by dip-coating.     

Study on inverse spinel zinc stannate, Zn2SnO4, as transparent conductive films deposited by rf magnetron sputtering

Inverse spinel zinc stannate (Zn₂SnO₄, ZTO) films were deposited onto fused quartz glass substrates heated at 800 °C by rf magnetron sputtering using a ceramic ZTO target (Zn:Sn = 2:1). H₂ flow ratios [H₂/(Ar + H₂)] were controlled from 0 to 30% during the depositions. ZTO films deposited at 800 °C possessed a polycrystalline inverse spinel structure. The lowest resistivity of 1.1 × 10^− 2 Ω cm was obtained for a ZTO film deposited at 20% H₂ flow ratio. The transmittance of the ZTO film was approximately 80% in the visible region.     

Optical and electrical properties of vapour phase grown Zn1 − xCrxTe crystals

The optical and electrical properties of vapour phase grown crystals of diluted magnetic semiconductor Zn_1 − xCr_xTe were investigated for 0 ≤ x ≤ 0.005. The diffuse reflectance spectra exhibited an increase in the fundamental absorption edge (E₀) with composition x and were also dominated by a broad absorption band around 5200 cm^− 1 arising from ⁵T₂ → ⁵E transition. The ⁵T₂ and ⁵E levels originate from the crystal field splitting of the ⁵D free ion in the ground state. The electrical resistivity measurements revealed semiconducting behaviour of the samples with p-type conductivity in the temperature range of 200-450 K.     

Effect of CuO addition to Nd(Zn1/2Ti1/2)O3 ceramics on sintering behavior and microwave dielectric properties

The microwave dielectric properties and microstructures of CuO-doped Nd(Zn_1/2Ti_1/2)O₃ ceramics prepared by the conventional solid-state route were investigated. The prepared Nd(Zn_1/2Ti_1/2)O₃ exhibits a mixture of Zn and Ti showing 1:1 order in the B-site. As an appropriate sintering aid, not only did CuO lower the sintering temperature, it could effectively hold back the evaporation of Zn in the Nd(Zn_1/2Ti_1/2)O₃. Moreover, CuO only resided in boundaries, which was confirmed by EDX analysis. The measured lattice parameters of CuO-doped Nd(Zn_1/2Ti_1/2)O₃ (a = 5.4652 ± 0.0005 ?, b = 5.6399 ± 0.0007 ?, c = 7.7797 ± 0.0008 ? and β = 90.01 ± 0.01°) retained identical to that of the pure Nd(Zn_1/2Ti_1/2)O₃ in all cases. In comparison with the pure Nd(Zn_1/2Ti_1/2)O₃ ceramics, specimen with 1 wt.% CuO addition possesses a compatible combination of dielectric properties with a ε_r of 30.68, a Q × f of 158,000 GHz (at 8 GHz) and a τ_f of − 45 ppm/°C at 1270 °C. It also indicated a 60 °C lowering in the sintering temperature. The proposed dielectrics can be a very promising candidate material for microwave or millimeter wave applications requiring extremely low dielectric loss.     

Structure and thermal conductivity of Gd2(TixZr1 − x)2O7 ceramics

The Gd₂(Ti_xZr_1 − x)₂O₇ (x = 0, 0.25, 0.50, 0.75, 1.00) ceramics were synthesized by solid state reaction at 1650 °C for 10 h in air. The relative density and structure of Gd₂(Ti_xZr_1 − x)₂O₇ were analyzed by the Archimedes method and X-ray diffraction. The thermal diffusivity of Gd₂(Ti_xZr_1 − x)₂O₇ from room temperature to 1400 °C was measured by a laser-flash method. The Gd₂Zr₂O₇ has a defect fluorite-type structure; however, Gd₂(Ti_xZr_1 − x)₂O₇ (0.25 ≤ x ≤ 1.00) compositions exhibit an ordered pyrochlore-type structure. Gd₂Zr₂O₇ and Gd₂Ti₂O₇ are infinitely soluable. The thermal conductivity of Gd₂(Ti_xZr_1 − x)₂O₇ increases with increasing Ti content under identical temperature conditions. The thermal conductivity of Gd₂(Ti_xZr_1 − x)₂O₇ first decreases gradually with the increase of temperature below 1000 °C and then increases slightly above 1000 °C. The thermal conductivity of Gd₂(Ti_xZr_1 − x)₂O₇ is within the range of 1.33 to 2.86 W m^− 1 K^− 1 from room temperature to 1400 °C.     

Synthesis and spectroscopic investigations of Mn3O4 nanoparticles

Trimanganese tetraoxide (Mn₃O₄) nanoparticles have been synthesized via hydrothermal process. Nevertheless, homogeneous nanoparticles of Mn₃O₄ with platelet lozange shape were obtained. The crystallite size ranged from 40 to 70 nm. The Mn₃O₄ product was investigated by X-ray diffraction, transmission electron microscopy (MET), and impedance spectroscopy. Electrical conductivity measurements showed that the as-synthesized Mn₃O₄ nanomaterial has a conductivity value which goes from 1.8 10⁻⁷ Ω⁻¹ cm⁻¹ at 298 K, to 23 10⁻⁵ Ω⁻¹ cm⁻¹ at 493 K. The temperature dependence of the conductivity between 298 and 493 K obeys to Arrhenius law with an activation energy of 0.48 eV.     

Thermal and mechanical properties of novel substrate crystal Mg0.4Al2.4O4

Mg_0.4Al_2.4O₄ single crystal was grown by the Czochralski method. The measured specific heat values are 0.804-1.06 J g^− 1 K^− 1 in the temperature range from 298.15 to 573.15 K. The calculated thermal conductivity components are 11.37, 11.47 and 10.77 W m^− 1 K^− 1 along the [111], [004] and [22?0] direction at 298.15 K. The Vickers microhardness values are 1328-1414 kg mm^− 2. These experimental results show that Mg_0.4Al_2.4O₄ crystal is a promising substrate for GaN-based LEDs.     

Electrical conductivity of 5 mol.% Yb2O3 and 5 mol.% Gd2O3 co-doped Sm2Zr2O7

Sm₂Zr₂O₇ co-doped with and without 5 mol.% Yb₂O₃ and 5 mol.% Gd₂O₃ were prepared by a pressureless-sintering method at 1973 K for 10 h in air. The relative density, structure and electrical conductivity were investigated by the Archimedes method, X-ray diffraction, scanning electron microscopy and impedance spectra measurements. Both Sm₂Zr₂O₇ and (Sm_0.9Gd_0.05Yb_0.05)₂Zr₂O₇ ceramics exhibit a single phase of pyrochlore-type structure. The grain conductivity, grain-boundary conductivity and total conductivity obey the Arrhenius relation, respectively, and gradually increase with increasing temperature from 723 to 1173 K. (Sm_0.9Gd_0.05Yb_0.05)₂Zr₂O₇ ceramic is the oxide-ion conductor in an oxygen partial pressure range of 1.0 × 10⁻⁴ to 1.0 atm at all test temperature levels. The grain conductivity, grain-boundary conductivity and total conductivity of (Sm_0.9Gd_0.05Yb_0.05)₂Zr₂O₇ with dual Yb³⁺ + Gd³⁺ doping are higher than those of undoped Sm₂Zr₂O₇ at identical temperature levels.     

The effect of In ion on the optical characteristics of Er in Er/Yb:LiNbO3 crystal

The effect of In³⁺ ion on the optical characteristics of Er³⁺ ion in Er/Yb:LiNbO₃ crystal under 980 nm excitation has been investigated. The Er and Yb contents in the crystals were measured by an inductively coupled plasma atomic emission spectrometer (ICP-AES). A significant enhancement of 1.54 μm emission was observed for Er/Yb:LiNbO₃ crystal doped with 1 mol% In₂O₃. The studies on the UV-vis absorption and the OH⁻ absorption spectra indicate that the threshold concentration of In³⁺ ion decreases with the Er/Yb doping in Er/Yb/In:LiNbO₃ crystal. The 1 mol% In₂O₃ doping results in the reduction of absorption cross section in the UV-vis region, meaning the formation of Er³⁺ cluster sites. The enhancement of 1.54 μm emission is attributed to the larger probabilities of the cross relaxation processes ⁴S_3/2 + ⁴I_15/2 → ⁴I_9/2 + ⁴I_13/2 (Er), ⁴S_3/2 + ⁴I_15/2 → ⁴I_13/2 + ⁴I_9/2 (Er) and ⁴I_9/2 + ⁴I_15/2 → ⁴I_13/2 + ⁴I_13/2 (Er) induced by Er³⁺ cluster sites.     

Varistor properties of ZnO-Pr6O11-CoO-Cr2O3-Y2O3-In2O3 ceramics

The varistor properties of the ZnO-Pr₆O₁₁-CoO-Cr₂O₃-Y₂O₃-In₂O₃ ceramics were investigated for different concentrations of In₂O₃. The increase of In₂O₃ concentration slightly increased the sintered density (5.60-5.63 g/cm³) and slightly decreased the average grain size (3.4-2.9 μm). The breakdown field increased from 6023 to 14822 V/cm with increasing concentration of In₂O₃. The nonlinear coefficient increased from 17.6 to 44.6 for up to 0.005 mol%, whereas the further doping caused it to decrease to 36.8. In₂O₃ acted as an acceptor due to the donor concentration, which decreases in the range of 1.02 × 10¹⁷ to 0.24 × 10¹⁷/cm³ with increasing concentration of In₂O₃.     

Synthesis and nano-field-effect transistors of p-type Zn0.3Cd0.7Te nanoribbons

Ternarysemiconductor Zn_0.3Cd_0.7Te nanoribbons are, firstly, synthesized via a two-step process, and the structure characterizations reveal that the as-synthesized nanoribbons are single-crystalline with a zinc blende structure and a crystal growth direction of [1-10]. Nano-field-effect transistors are fabricated based on single nanoribbon, and the electron transport characteristics demonstrate that the Zn_0.3Cd_0.7Te ribbons have p-type conductivity with a mobility (μ_h) of 5.7 cm²V⁻¹S⁻¹ and carrier concentration (n_h) about 1.1 × 10¹⁷ cm⁻³. The prepared nanoribbons with significant p-type conductivity will be a very attractive candidate for nanoelectronic devices.     

Influence of ZnO additive on the properties of Y-doped BaSnO3 proton conductor

The effects of ZnO additive on the phase formation, microstructure and electrical conduction of Y-doped BaSnO₃ have been investigated. The single-phase and dense BaSn_0.75Y_0.25O_3−δ compound with 4 mol% ZnO additive was successfully prepared after sintering at 1300 °C, which significantly reduces the sintering temperature. The conductivities measured under dry and wet air atmospheres reveal that the bulk conductivity of BaSn_0.71Y_0.25Zn_0.04O_3−δ is much lower than that of BaSn_0.75Y_0.25O_3−δ. However, ZnO as a sintering aid does not affect the bulk conductivity. The total conductivity of BaSn_0.75Y_0.25O_3−δ with ZnO as the sintering aid is slightly higher than that of unmodified BaSn_0.75Y_0.25O_3−δ, and reaches 2.4 × 10⁻³ S cm⁻¹ at 621 °C. Therefore, this material can be used as a proton-conducting electrolyte for intermediate temperature solid oxide fuel cells.     

Microstructure and optical properties of MgxZn1−xO thin films grown by means of pulsed laser deposition

The single-phase epitaxial Mg_xZn_1−xO (0.4 < x < 0.9) alloy films with wide band gap have been deposited on cubic LaAlO₃ (LAO) (100) substrates by pulsed laser deposition (PLD). X-ray diffraction measurement and TEM photograph indicate that the cubic phase could be stabilized up to Zn content about 0.6 without any phase separation. Films and substrates have a good heteroepitaxial relationship of (100) _MgxZn1−xO||(100)_LAO (out-of-plane) and (011)_MgxZn1−xO||(010)_LAO (in-plane)_. The lattice parameters a of Mg_xZn_1−xO films increase almost linearly with increasing ZnO composition, while the band gap energy of the materials increases from 5.17 to 5.27 eV by alloying with more MgO. The cross-section morphology reveals layer thickness of about 250-300 nm and AFM scan over a 30 μm × 30 μm area reveals a surface roughness R_a of about 100 nm.     

Fabrication of highly conductive Ta-doped SnO2 polycrystalline films on glass using seed-layer technique by pulse laser deposition

We discuss the fabrication of highly conductive Ta-doped SnO₂ (Sn_1 − xTa_xO₂; TTO) thin films on glass by pulse laser deposition. On the basis of the comparison of X-ray diffraction patterns and resistivity (ρ) values between epitaxial films and polycrystalline films deposited on bare glass, we proposed the use of seed-layers for improving the conductivity of the TTO polycrystalline films. We investigated the use of rutile TiO₂ and NbO₂ as seed-layers; these are isostructural materials of SnO_2, which are expected to promote epitaxial-like growth of the TTO films. The films prepared on the 10-nm-thick seed-layers exhibited preferential growth of the TTO (110) plane. The TTO film with x = 0.05 on rutile TiO₂ exhibited ρ  = 3.5 × 10^− 4 Ω cm, which is similar to those of the epitaxial films grown on Al₂O₃ (0001).     

Enhanced conductivity of pulsed laser deposited n-InGaZn6O9 films and its rectifying characteristics with p-SiC

Wide band gap InGaZn₆O₉ films of thickness ~ 350 nm were deposited on sapphire (0001) at room temperature by using the pulsed laser deposition technique. The transparent films showed the optical transmission of > 80% with the room temperature Hall mobility of ~ 10 cm²/V s and conductivity of 4 × 10² S/cm at a carrier density > 10²⁰ cm^− 3. The electrical properties as a function of deposition temperatures revealed that the conductivity and mobility almost retained up to the deposition temperature of 200 °C. The films annealed in different atmospheres suggested oxygen vacancy plays an important role in determining the electrical conductivity of the compound. Room temperature grown heterostructure of n-InGaZn₆O₉/p-SiC showed a good rectifying behavior with a leakage current density of less than 10^− 9 A/cm², current rectifying ratio of 10⁵ with a forward turn on voltage ~ 3 V, and a breakdown voltage greater than 32 V.     

ZnO and Zn1−xCdxO nanocrystallites obtained by oxidation of precursor Langmuir-Blodgett multilayers

ZnO and Zn_1−xCd_xO nanocrystallites were prepared by oxidation of zinc arachidate-arachidic acid and zinc arachidate-cadmium arachidate-arachidic acid LB multilayers, respectively. The metal content of the multilayers was controlled by manipulation of subphase composition and pH. Precursor multilayers were oxidized in the temperature range of 400 °C-700 °C. The formation of ZnO and Zn_1−xCd_xO was confirmed by UV-Visible spectroscopy. Uniformly distributed, isolated and nearly mono-dispersed nanocrystallites of ZnO (11 ± 3 nm) and Zn_1−xCd_xO (18 ± 6 nm) were obtained.     

Structural,optical and electrical properties of In4Sn3O12 films prepared by pulsed laser deposition

Highly conducting (σ ∼ 2.6 × 10³ Ω⁻¹ cm⁻¹) In₄Sn₃O₁₂ films have been deposited using pulsed laser deposition (PLD) on glass and quartz substrates held at temperatures between 350 and 550 °C under chamber pressures of between 2.5 and 15 mTorr O₂. The crystallinity and the surface roughness of the films were found to increase with increasing substrate temperature. Electron concentrations of the order of 5 × 10²⁰ cm⁻³ and mobilities as high as 30 cm² V⁻¹ s⁻¹ were determined from Hall effect measurements performed on the films. Fitting of the transmission spectral profiles in the ultra-violet–visible spectrum has allowed the determination of the refractive index and extinction coefficient for the films. A red-shift in the frequency of plasmon resonance is observed with both increasing substrate temperature and oxygen pressure. Effective masses have been derived from the plasma frequencies and have been found to increase with carrier concentration indicating a non-parabolic conduction band in the material In₄Sn₃O₁₂. The optical band-gap has been determined as 3.8 eV from the analysis of the absorption edge in the UV. These results highlight the potential of these films as lower In-content functional transparent conducting materials.