The Effects of Zr Doping on the Optical,Electrical and Microstructural Properties of Thin ZnO Films Deposited by Atomic Layer Deposition

Transparent conducting oxides (TCOs), with high optical transparency (≥85%) and low electrical resistivity (10⁻⁴ Ω·cm) are used in a wide variety of commercial devices. There is growing interest in replacing conventional TCOs such as indium tin oxide with lower cost, earth abundant materials. In the current study, we dope Zr into thin ZnO films grown by atomic layer deposition (ALD) to target properties of an efficient TCO. The effects of doping (0–10 at.% Zr) were investigated for ~100 nm thick films and the effect of thickness on the properties was investigated for 50–250 nm thick films. The addition of Zr⁴⁺ ions acting as electron donors showed reduced resistivity (1.44 × 10⁻³ Ω·cm), increased carrier density (3.81 × 10²⁰ cm⁻³), and increased optical gap (3.5 eV) with 4.8 at.% doping. The increase of film thickness to 250 nm reduced the electron carrier/photon scattering leading to a further reduction of resistivity to 7.5 × 10⁻⁴ Ω·cm and an average optical transparency in the visible/near infrared (IR) range up to 91%. The improved n-type properties of ZnO: Zr films are promising for TCO applications after reaching the targets for high carrier density (>10²⁰ cm⁻³), low resistivity in the order of 10⁻⁴ Ω·cm and high optical transparency (≥85%).     

Normally-off Hydrogen-Terminated Diamond Field-Effect Transistor with SnOx Dielectric Layer Formed by Thermal Oxidation of Sn

SnO_x films were deposited on a hydrogen-terminated diamond by thermal oxidation of Sn. The X-ray photoelectron spectroscopy result implies partial oxidation of Sn film on the diamond surface. The leakage current and capacitance–voltage properties of Al/SnO_x/H-diamond metal-oxide-semiconductor diodes were investigated. The maximum leakage current density value at −8.0 V is 1.6 × 10⁻⁴ A/cm², and the maximum capacitance value is measured to be 0.207 μF/cm². According to the C–V results, trapped charge density and fixed charge density are determined to be 2.39 × 10¹² and 4.5 × 10¹¹ cm⁻², respectively. Finally, an enhancement-mode H-diamond field effect transistor was obtained with a V_TH of −0.5 V. Its I_DMAX is −21.9 mA/mm when V_GS is −5, V_DS is −10 V. The effective mobility and transconductance are 92.5 cm²V⁻¹ s⁻¹ and 5.6 mS/mm, respectively. We suspect that the normally-off characteristic is caused by unoxidized Sn, whose outermost electron could deplete the hole in the channel.     

Nickel Oxide Films Deposited by Sol-Gel Method: Effect of Annealing Temperature on Structural,Optical, and Electrical Properties

In our study, transparent and conductive films of NiO_x were successfully deposited by sol-gel technology. NiO_x films were obtained by spin coating on glass and Si substrates. The vibrational, optical, and electrical properties were studied as a function of the annealing temperatures from 200 to 500 °C. X-ray Photoelectron (XPS) spectroscopy revealed that NiO was formed at the annealing temperature of 400 °C and showed the presence of Ni⁺ states. The optical transparency of the films reached 90% in the visible range for 200 °C treated samples, and it was reduced to 76–78% after high-temperature annealing at 500 °C. The optical band gap of NiOx films was decreased with thermal treatments and the values were in the range of 3.92–3.68 eV. NiO_x thin films have good p-type electrical conductivity with a specific resistivity of about 4.8 × 10⁻³ Ω·cm. This makes these layers suitable for use as wideband semiconductors and as a hole transport layer (HTL) in transparent solar cells.     

Biopolymer-Based Films from Sodium Alginate and Citrus Pectin Reinforced with SiO2

Blend films based on sodium alginate (SA) and citrus pectin (P) reinforced with different concentrations of SiO₂ (0–10% w/w) were developed in this study. From the morphological (SEM) and structural (FT-IR) evaluation, it was verified that the incorporation of the reinforcing agent did not drastically modify the microstructure of the films, nor did new chemical bonds form. However, the XRD results suggested a slight reduction in the crystallinities of the blends by the incorporation of SiO₂. Among the formulations prepared, the addition of a 5% reinforcing agent was responsible for the simultaneous improvement of mechanical and barrier properties. Comparing the control sample (SA/P) with the SA/P/5.0%SiO₂ film, the tensile strength increased from 27.7 ± 3.7 to 40.6 ± 4.5 MPa, and the water-vapor transmission rate decreased from 319.8 ± 38.7 to 288.9 ± 23.5 g m⁻² day⁻¹. Therefore, SiO_2, as a reinforcing agent in SA/P blends, represents a simple and effective strategy for improving the properties of biopolymer-based films in applications, such as packaging.     

Sustainable Chitosan-Dialdehyde Cellulose Nanocrystal Film

In this study, we incorporated 2,3-dialdehyde nanocrystalline cellulose (DANC) into chitosan as a reinforcing agent and manufactured biodegradable films with enhanced gas barrier properties. DANC generated via periodate oxidation of cellulose nanocrystal (CNC) was blended at various concentrations with chitosan, and bionanocomposite films were prepared via casting and characterized systematically. The results showed that DANC developed Schiff based bond with chitosan that improved its properties significantly. The addition of DANC dramatically improved the gas barrier performance of the composite film, with water vapor permeability (WVP) value decreasing from 62.94 g·mm·m⁻²·atm⁻¹·day⁻¹ to 27.97 g·mm·m⁻²·atm⁻¹·day⁻¹ and oxygen permeability (OP) value decreasing from 0.14 cm³·mm·m⁻²·day⁻¹·atm⁻¹ to 0.026 cm³·mm·m⁻²·day⁻¹·atm⁻¹. Meanwhile, the maximum decomposition temperature (Td_max) of the film increased from 286 °C to 354 °C, and the tensile strength of the film was increased from 23.60 MPa to 41.12 MPa when incorporating 25 wt.% of DANC. In addition, the chitosan/DANC (75/25, wt/wt) films exhibited superior thermal stability, gas barrier, and mechanical strength compared to the chitosan/CNC (75/25, wt/wt) film. These results confirm that the DANC and chitosan induced films with improved gas barrier, mechanical, and thermal properties for possible use in film packaging.     

Synthesis of High Crystallinity 1.13 nm Tobermorite and Xonotlite from Natural Rocks,Their Properties and Application for Heat-Resistant Products

The main measure to reduce energy losses is the usage of insulating materials. When the temperature exceeds 500 °C, silicate and ceramic products are most commonly used. In this work, high-crystallinity 1.13 nm tobermorite and xonotlite were hydrothermally synthesized from lime and Ca–Si sedimentary rock, opoka. By XRD, DSC, TG and dilatometry methods, it has been shown that 1.13 nm tobermorite becomes the predominant compound in stirred suspensions at 200 °C after 4 h of synthesis in the mixture with a molar ratio CaO/SiO₂ = 0.83. It is suitable for the production of insulating products with good physical–mechanical properties (average density < 200 kg·m⁻¹, compressive strength ~0.9 MPa) but has a limited operating temperature (up to 700 °C). Sufficiently pure xonotlite should be used to obtain materials with a higher operating temperature. Even small amounts of semi-amorphous C–S–H(I) significantly increase its linear shrinkage during firing. It has also been observed that an increase in the strength values of the samples correlated well with the increase in the size of xonotlite crystallites. The optimal technological parameters are as follows: molar ratio of mixture CaO/SiO₂ = 1.2; water/solid ratio W/S = 20.0; duration of hydrothermal synthesis at 220 °C—8 h, duration of autoclaving at 220 °C—4 h. The average density of the samples was ~180 kg·m⁻¹, the operating temperature was at least 1000 °C, and the compressive strengths exceeded 1.5 MPa.     

Enhanced Corrosion Resistance of Layered Double Hydroxide Films on Mg Alloy: The Key Role of Cationic Surfactant

In this study, dense anticorrosion magnesium–aluminum layered double hydroxide (MgAl-LDH) films were prepared for the first time by introducing a cationic surfactant tetradecyltrimethyl ammonium bromide (TTAB) in the process of in situ hydrothermal synthesis of Mg-Al LDH films on an AZ31 magnesium alloy. Results of XRD, FTIR, and SEM confirmed that TTAB forms the MgAl-LDH-TTAB, although TTAB cannot enter into LDH layers, and MgAl-LDH-TTAB powders are much smaller and more homogenous than MgAl-CO₃²⁻-LDH powders. Results of SEM, EDS, mapping, and XPS confirmed that TTAB forms the MgAl-LDH-TTAB films and endows LDH films with denser structure, which provides films with better shielding efficiency. Results of potentiodynamic polarization curves (PDP) and electrochemical impedance spectroscopy (EIS) confirmed that MgAl-LDH-TTAB_{x g} films have better corrosion resistance than an MgAl-CO₃²⁻-LDH film. The corrosion current density (i_corr) of the MgAl-LDH-TTAB_{0.35 g} film in 3.5 wt.% NaCl solution was reduced to 1.09 × 10⁻⁸ A.cm⁻² and the |Z|_{f = 0.05 Hz} value was increased to 4.48 × 10⁵ Ω·cm². Moreover, the increasing concentration of TTAB in MgAl-LDH-TTAB_{x g} (x = 0.025, 0.05, 0.1, 0.2 and 0.35) provided denser outer layer LDH films and thereby increased the corrosion resistance of the AZ31 Mg alloy. Additionally, the |Z|_{f = 0.05 Hz} values of the MgAl-LDH-TTAB_{0.35 g} film still remained at 10⁵ Ω·cm² after being immersed in 3.5 wt.% NaCl solution for 168 h, implying the good long-term corrosion resistance of MgAl-LDH-TTAB_{x g} films. Therefore, introducing cationic surfactant in the process of in situ hydrothermal synthesis can be seen as a novel approach to creating efficient anticorrosion LDH films for Mg alloys.     

Solid-State-Activated Sintering of ZnAl2O4 Ceramics Containing Cu3Nb2O8 with Superior Dielectric and Thermal Properties

Low-temperature co-fired ceramics (LTCCs) are dielectric materials that can be co-fired with Ag or Cu; however, conventional LTCC materials are mostly poorly thermally conductive, which is problematic and requires improvement. We focused on ZnAl₂O₄ (gahnite) as a base material. With its high thermal conductivity (~59 W·m⁻¹·K⁻¹ reported for 0.83ZnAl₂O₄–0.17TiO₂), ZnAl₂O₄ is potentially more thermally conductive than Al₂O₃ (alumina); however, it sinters densely at a moderate temperature (~1500 °C). The addition of only 4 wt.% of Cu₃Nb₂O₈ significantly lowered the sintering temperature of ZnAl₂O₄ to 910 °C, which is lower than the melting point of silver (961 °C). The sample fired at 960 °C for 384 h exhibited a relative permittivity (ε_r) of 9.2, a quality factor by resonant frequency (Q × f) value of 105,000 GHz, and a temperature coefficient of the resonant frequency (τ_f) of −56 ppm·K⁻¹. The sample exhibited a thermal conductivity of 10.1 W·m⁻¹·K⁻¹, which exceeds that of conventional LTCCs (~2–7 W·m⁻¹·K⁻¹); hence, it is a superior LTCC candidate. In addition, a mixed powder of the Cu₃Nb₂O₈ additive and ZnAl₂O₄ has a melting temperature that is not significantly different from that (~970 °C) of the pristine Cu₃Nb₂O₈ additive. The sample appears to densify in the solid state through a solid-state-activated sintering mechanism.     

Phase Evaluation,Mechanical Properties and Thermal Behavior of Hot-Pressed LC-YSZ Composites for TBC Applications

In this work, La₂Ce₂O₇-yttria-stabilized zirconia (LC-YSZ) composites with different weight fractions of YSZ (40–70 wt.%) were prepared by hot pressing at 1400 °C and investigated as a material for thermal barrier-coating (TBC) applications. For this purpose, the effect of YSZ addition on the phase composition, microstructure, mechanical performance and thermal behavior was studied. X-ray diffraction analysis showed that the LC-YSZ composites were mainly composed of a cubic ZrO₂ and La₂O₃-CeO₂-ZrO₂ solid solution with a pyrochlore structure, indicating that the reaction between LC and YSZ took place during hot pressing. Scanning electron microscopy revealed the high microstructural stability of the prepared composites, as the pore formation was significantly controlled and a high relative density (>97%) was obtained. The microstructure of LC-YSZ bulk samples was relatively fine-grained, with an average grain size below or very close to 1 µm. YSZ doping improved the Vickers hardness of the LC-YSZ composites; the highest hardness, with value of 12 ± 0.62 GPa, was achieved for the composite containing 70 wt.% of YSZ. The fracture toughness of LC-YSZ composites was in the range from 2.13 to 2.5 MPa·m^1/2. No statistically significant difference in heat capacity or thermal conductivity was found between the composites with different content of YSZ. The results showed that LC-YSZ composites have relatively low thermal conductivities from room temperature (1.5–1.8 W·m⁻¹·K⁻¹) up to 1000 °C (2.5–3.0 W·m⁻¹·K⁻¹). This indicates that the prepared LC-YSZ composite materials are promising candidates for TBC applications.     

Effect of Nickel as Stress Factor on Phenol Biodegradation by Stenotrophomonas maltophilia KB2

This study focuses on the phenol biodegradation kinetics by Stenotrophomonas maltophilia KB2 in a nickel-contaminated medium. Initial tests proved that a nickel concentration of 33.3 mg·L⁻¹ caused a cessation of bacterial growth. The experiments were conducted in a batch bioreactor in several series: without nickel, at constant nickel concentration and at varying metal concentrations (1.67–13.33 g·m⁻³). For a constant Ni²⁺ concentration (1.67 or 3.33 g·m⁻³), a comparable bacterial growth rate was obtained regardless of the initial phenol concentration (50–300 g·m⁻³). The dependence µ = f (S₀) at constant Ni²⁺ concentration was very well described by the Monod equations. The created varying nickel concentrations experimental database was used to estimate the parameters of selected mathematical models, and the analysis included different methods of determining metal inhibition constant K_IM. Each model showed a very good fit with the experimental data (R² values were higher than 0.9). The best agreement (R² = 0.995) was achieved using a modified Andrews equation, which considers the metal influence and substrate inhibition. Therefore, kinetic equation parameters were estimated: µ_max = 1.584 h⁻¹, K_S = 185.367 g·m⁻³, K_IS = 106.137 g·m⁻³, K_IM = 1.249 g·m⁻³ and n = 1.0706.     

Effect of Sr Deficiency on Electrical Conductivity of Yb-Doped Strontium Zirconate

The effect of Sr-deficiency on microstructure, phase composition and electrical conductivity of Sr_xZr_0.95Yb_0.05O_3-δ (x = 0.94–1.00) was investigated via X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy and impedance spectroscopy. The samples were synthesized by a chemical solution method and sintered at 1600 °C. According to X-ray diffraction data, the samples with x = 0.96–1.00 were single-phase oxides possessing an orthorhombic perovskite-type structure; while zirconia-based minor phases arouse at x = 0.94, which was confirmed by the electron microscopy. Sr stoichiometry was shown to influence the electrical conductivity. The highest total and bulk conductivities, 6–10⁻⁴ Scm⁻¹ and 3–10⁻³ Scm⁻¹, respectively, at 600 °C in humid air (pH₂O = 3.2 kPa), were observed for the x = 0.98 composition. In the temperature range of 300–600 °C, the conductivity of the samples with x = 0.96–1.00 increased with the increase in humidity, which indicates a significant contribution of protonic defects to the charge transport. Electrical conductivity of Sr_xZr_0.95Yb_0.05O_3-δ was discussed in terms of the defect formation model and the secondary phases precipitation.     

Global cost estimates of reducing carbon emissions through avoided deforestation

Tropical deforestation is estimated to cause about one-quarter of anthropogenic carbon emissions, loss of biodiversity, and other environmental services. United Nations Framework Convention for Climate Change talks are now considering mechanisms for avoiding deforestation (AD), but the economic potential of AD has yet to be addressed. We use three economic models of global land use and management to analyze the potential contribution of AD activities to reduced greenhouse gas emissions. AD activities are found to be a competitive, low-cost abatement option. A program providing a 10% reduction in deforestation from 2005 to 2030 could provide 0.3–0.6 Gt (1 Gt = 1 × 10⁵ g) CO₂·yr⁻¹ in emission reductions and would require $0.4 billion to $1.7 billion·yr⁻¹ for 30 years. A 50% reduction in deforestation from 2005 to 2030 could provide 1.5–2.7 Gt CO₂·yr⁻¹ in emission reductions and would require $17.2 billion to $28.0 billion·yr⁻¹. Finally, some caveats to the analysis that could increase costs of AD programs are described.     

Investigation of the Optoelectronic Properties of Ti-doped Indium Tin Oxide Thin Film

In this study, direct-current magnetron sputtering was used to fabricate Ti-doped indium tin oxide (ITO) thin films. The sputtering power during the 350-nm-thick thin-film production process was fixed at 100 W with substrate temperatures increasing from room temperature to 500 °C. The Ti-doped ITO thin films exhibited superior thin-film resistivity (1.5 × 10⁻⁴ Ω/cm), carrier concentration (4.1 × 10²¹ cm⁻³), carrier mobility (10 cm²/Vs), and mean visible-light transmittance (90%) at wavelengths of 400–800 nm at a deposition temperature of 400 °C. The superior carrier concentration of the Ti-doped ITO alloys (>10²¹ cm⁻³) with a high figure of merit (81.1 × 10⁻³ Ω⁻¹) demonstrate the pronounced contribution of Ti doping, indicating their high suitability for application in optoelectronic devices.     

Comparison of Different Cermet Coatings Sprayed on Magnesium Alloy by HVOF

In the present study, two different cermet coatings, WC–CrC–Ni and Cr₃C₂–NiCr, manufactured by the high-velocity oxy-fuel (HVOF) method were studied. They are labeled as follows: WC–CrC–Ni coating—WC and Cr₃C₂–NiCr coating—CrC. These coatings were deposited onto a magnesium alloy (AZ31) substrate. The goal of the study was to compare these two types of cermet coating, which were investigated in terms of microstructure features and selected mechanical properties, such as hardness, instrumented indentation, fracture toughness, and wear resistance. The results reveal that the WC content influenced the hardness and Young’s modulus. The most noticeable effect of WC addition was observed for the wear resistance. WC coatings had a wear intensity value that was almost two times lower, equal to 6.5·10⁻⁶ mm³/N·m, whereas for CrC ones it was equal to 12.6·10⁻⁶ mm³/N·m. On the other hand, the WC coating exhibited a lower value of fracture toughness.     

Linking the Electrical Conductivity and Non-Stoichiometry of Thin Film Ce1−xZrxO2−δ by a Resonant Nanobalance Approach

Bulk ceria-zirconia solid solutions (Ce_1−xZr_xO_2−δ, CZO) are highly suited for application as oxygen storage materials in automotive three-way catalytic converters (TWC) due to the high levels of achievable oxygen non-stoichiometry δ. In thin film CZO, the oxygen storage properties are expected to be further enhanced. The present study addresses this aspect. CZO thin films with 0 ≤ x ≤ 1 were investigated. A unique nano-thermogravimetric method for thin films that is based on the resonant nanobalance approach for high-temperature characterization of oxygen non-stoichiometry in CZO was implemented. The high-temperature electrical conductivity and the non-stoichiometry δ of CZO were measured under oxygen partial pressures pO₂ in the range of 10⁻²⁴–0.2 bar. Markedly enhanced reducibility and electronic conductivity of CeO₂-ZrO₂ as compared to CeO_2−δ and ZrO₂ were observed. A comparison of temperature- and pO₂-dependences of the non-stoichiometry of thin films with literature data for bulk Ce_1−xZr_xO_2−δ shows enhanced reducibility in the former. The maximum conductivity was found for Ce_0.8Zr_0.2O_2−δ, whereas Ce_0.5Zr_0.5O_2-δ showed the highest non-stoichiometry, yielding δ = 0.16 at 900 °C and pO₂ of 10⁻¹⁴ bar. The defect interactions in Ce_1−xZr_xO_2−δ are analyzed in the framework of defect models for ceria and zirconia.     

Microstructure and Wear Properties of Laser Cladding WC/Ni-Based Composite Layer on Al–Si Alloy

The microstructural and wear properties of laser-cladding WC/Ni-based layer on Al–Si alloy were investigated by scanning electron microscope (SEM), X-ray diffraction (XRD), energy dispersive spectrometer (EDS) and wear-testing. The results show that, compared with the original specimen, the microhardness and wear resistance of the cladding layer on an Al–Si alloy were remarkably improved, wherein the microhardness of the layer achieved 1100 HV and the average friction coefficient of the layer was barely 0.14. The mainly contributor to such significant improvement was the generation of a WC/Ni-composite layer of Al–Si alloy during laser cladding. Two types of carbides, identified as M₇C₃ and M₂₃C₆, were found in the layer. The wear rate of the layer first increased and then decreased with the increase in load; when the load was 20 N, 60 N and 80 N, the wear rate of layer was1.89 × 10⁻³ mm³·m⁻¹, 3.73 × 10⁻³ mm³·m⁻¹ and 2.63 × 10⁻³ mm³·m⁻¹, respectively, and the average friction coefficient (0.14) was the smallest when the load was 60 N.     

A High-Strain-Rate Superplasticity of the Al-Mg-Si-Zr-Sc Alloy with Ni Addition

The current study analyzed the effect of Ni content on the microstructure and superplastic deformation behavior of the Al-Mg-Si-Cu-based alloy doped with small additions of Sc and Zr. The superplasticity was observed in the studied alloys due to a bimodal particle size distribution. The coarse particles of eutectic origin Al₃Ni and Mg₂Si phases with a total volume fraction of 4.0–8.0% and a mean size of 1.4–1.6 µm provided the particles with a stimulated nucleation effect. The L1₂– structured nanoscale dispersoids of Sc- and Zr-bearing phase inhibited recrystallization and grain growth due to a strong Zener pinning effect. The positive effect of Ni on the superplasticity was revealed and confirmed by a high-temperature tensile test in a wide strain rate and temperature limits. In the alloy with 4 wt.% Ni, the elongation-to-failure of 350–520% was observed at 460 °C, in a strain rate range of 2 × 10⁻³–5 × 10⁻² s⁻¹.     

Construction of TiO2-Eggshell for Efficient Degradation of Tetracycline Hydrochloride: Sunlight Induced In-Situ Formation of Carbonate Radical

Photocatalytic degradation of an antibiotic by utilizing inexhaustible solar energy represents an ideal solution for tackling global environment issues. The target generation of active oxidative species is highly desirable for the photocatalytic pollutants degradation. Herein, aiming at the molecular structure of tetracycline hydrochloride (TC), we construct sunlight-activated high-efficient catalysts of TiO₂-eggshell (TE). The composite ingeniously utilizes the photoactive function of TiO₂ and the composition of eggshell, which can produce oxidative ·CO₃⁻ species that are especially active for the degradation of aromatic compounds containing phenol or aniline structures. Through the synergistic oxidation of the··CO₃⁻ with the traditional holes (h⁺), superoxide radicals (·O²⁻) and hydroxyl radicals (·OH) involved in the photocatalytic process, the optimal TE photocatalyst degrades 92.0% TC in 30 min under solar light, which is higher than TiO₂ and eggshell. The photocatalytic degradation pathway of TC over TE has been proposed. The response surface methodology is processed by varying four independent parameters (TC concentration, pH, catalyst dosage and reaction time) on a Box–Behnken design (BBD) to optimize the experimental conditions. It is anticipated that the present work can facilitate the development of novel photocatalysts for selective oxidation based on ·CO₃⁻.     

Oxidation Mechanism of Al-Sn Bearing Alloys

Oxidation of Al-Sn bearing alloy occurs during production, processing and use, which reduces both alloy performance and performance of coatings applied to the alloy surface. Therefore, the oxidation mechanism of Al-Sn bearing alloy is studied at 25, 180, 300, and 500 °C. The oxidation morphologies of the alloy were observed by scanning electron microscopy (SEM), and the oxidation products were determined by X-ray diffraction (XRD). The oxidation weight gain curves were obtained by thermogravimetric analysis. The experimental results show that: Al-Sn bearing alloy is oxidized quickly to form Al₂O₃. As the oxidation temperature increases, Sn phase start to precipitate along the grain boundary and form networked spheroids of Sn on the alloy surface. The amount of precipitation increases with further increase of the oxidation temperature. Cracks and holes are left in the alloy. The oxide layer is mainly composed of Sn, SnO₂, and Al₂O₃. At 25 °C, oxidation rate of Al-Sn alloy approach zero. At 180, 300, and 500 °C, the oxidation rate increases quickly conforming to a power function, and eventually remains stable at about 3 × 10⁻⁶ mg·mm⁻²·s⁻¹.     

Synthesis and Characterization of Al- and SnO2-Doped ZnO Thermoelectric Thin Films

The effect of SnO₂ addition (0, 1, 2, 4 wt.%) on thermoelectric properties of c-axis oriented Al-doped ZnO thin films (AZO) fabricated by pulsed laser deposition on silica and Al₂O₃ substrates was investigated. The best thermoelectric performance was obtained on the AZO + 2% SnO₂ thin film grown on silica, with a power factor (PF) of 211.8 μW/m·K² at 573 K and a room-temperature (300 K) thermal conductivity of 8.56 W/m·K. PF was of the same order of magnitude as the value reported for typical AZO bulk material at the same measurement conditions (340 μW/m·K²) while thermal conductivity κ was reduced about four times.