Warawoot Thowladda

Preparation, Characterization and Finite Element Computation of Cu(Al1/2Fe1/2)O2 Delafossite-Oxide Themoelectric Generator Module

The CuAl1/2Fe1/2O2 delafossite oxide has been synthesized by solid state reaction method for studying thermoelectric properties and measuring thermoelectric generator output electric power. The Finite Element technique was used to compute the output voltage of thermoelectric generator in applying temperature difference on a single bar and a module model with compared to the measurement results. The measurement results of positive sign Seebeck coefficient confirm the p-type conductor of the sample. The properties of Seebeck coefficient, electrical conductivity, and thermal conductivity are range from 260 to 310μV/K, from 7 to16 S/cm and from 2.5 to 3.5 W/cm-K,respectively, in the temperature range of 300 to 960 K. The output voltage of the single bar in dimension 4.2 × 2.5 × 20 mm3 obtained 0.5 to 3 mV on applying temperature difference from 1 to 10 K closely to the Finite Element result. The computing results of the thermoelectric single bar and module in high temperature reveal the output electric voltage of CuAl1/2Fe1/2O2 oxide raises with the temperature and the number of thermoelectric leg increase. In important results, the high value of electric voltage is obtained 0.2 and 0.4 V for the single bar and the module at 950 K.

Thermoelectric Properties of Sn2+-Substituted CuFeO2 Delafossite-Oxide

This study aims to investigate the effect of the Sn2+-substituted into the CuFeO2 delafossite on thermoelectric properties in the Sn content of x = 0.03, 0.05. The CuFe1−xSnxO2 samples were synthesized by solid state reaction. The crystal structure was characterized by XRD, TGA, XPS and the thermoelectric properties were measured in the range of 300 to 960 K. The Seebeck coefficient display positive sign in all temperature range and the XPS show the stable Sn+2 state as confirming the Sn-doped CuFeO2 playing p-type conductor. The Sn2+-substituted supports the mixed valency Fe3+/Fe4+ state in transition octahedral oxide of FeO6 layer enhancing Seebeck coefficient. The high Seebeck are appeared in content of x=0.03 which are 280 to 340 µV/K in the range of 300 to 800 K. The experimental Seebeck corresponds to the prediction formula at high temperature. Totally, the maximum Power Factor is 2.30×10−4 W/mK2 occurring in the CuFe0.95Sn0.05O2 at 860 K which is higher than that value of the undoped-CuFeO2 in 4 times. These support that the Sn-substituted CuFeO2 delafossite enhancing thermoelectric properties.

Synthesis and Characterization of Cu-Doped SnO2 Thin Films by Aerosol Pyrolysis Technique for Gas Sensor Application

Thin films of un-doped and Cu-doped tin oxide were synthesized on quartz substrates by the purpose-built aerosol pyrolysis apparatus from 0.2 M SnCl4.5H2O – ethanol solution. CuCl2.2H2O was used as a source of Cu dopant. The Cu dopant of 1, 3 and 5 wt.% were used for doping SnO2 film. The morphological, structural, optical and electrical properties under the influence of the Cu-doping was examined by FE-SEM, XRD, UV-Vis transmission spectroscopy and Hall effect measurement technique. XRD patterns of all films exhibited rutile-phase SnO2. The doping content of 1%Cu improved the film crystallinity. The Cu doping content decreased optical bandgap from 4.36 eV for undoped SnO2 to 4.28 eV for 3%Cu-doped SnO2. The further Cu doping content increased the bandgap energy to 4.32 eV. The resistivity was increased for doping of Cu 1% but it was decreased with further increasing in Cu-doping contents

Effects of Air Exposure Time and Annealing Temperature on Superhydrophobic Surface of Titanium Dioxide Films

TiO2 thin films coated on glass substrates for self-cleaning applications were prepared by sol-gel dip-coating technique. The influence of annealing temperature and air exposure time on wettability was investigated by a water contact-angle measurement. Thermal annealing at temperatures of 100, 200 and 300 °C in air were conducted to the films. Surface morphology of the films was observed by FE-SEM. Elemental distribution and optical properties were examined by EDX mapping and UV-Vis transmission spectroscopy, respectively. Atomic bonding was confirmed by FTIR. The contact angle reached a maximum when the films were annealed at 200 °C. The contact angles of the as-synthesized films were 61.4±2.7°. During storage in air for 20 days, the contact angles increased to 143.1±2.1°. The films were further reannealed with 100 °C for 20 min, the contact angles were enhanced to 153.1±1.3°. The association of contact angle among the surface morphology, elemental distribution and atomic bonding of the films will be discussed.

Effect of SnCl4 Concentration on Transparent and Conducting Undoped Tin Oxide Thin Films

The purpose-built pyrolysis system based on an ultrasonically generated aerosol has been successfully used for deposition of highly transparent and conductive undoped tin (IV) oxide thin films. The morphological, structural, optical and electrical properties as well as electronic structures of the films for different concentrations of SnCl4.5H2O used as the starting precursor were investigated. FE-SEM displayed the substrate surfaces were uniformly covered with the film. The film thickness varied with the precursor concentration. XRD patterns showed the deposited films were a tetragonal phase and presented random orientations. The optical transmission spectra of all films revealed highly transmittance in the visible region. Refractive index of the films was between 1.85 and 2.0. XPS spectra for the Sn 3d5/2 and Sn 3d3/2 confirmed that the films were composed of SnO and SnO2 phases. The non-stoichiometric composition decreased with increasing concentration of the precursor. The films deposited with 0.30 M showed the highest conductivity and carrier concentration of 17 W-1cm-1 and 9.5 x 1019 cm-3, respectively. The disagreement of relation between XPS and Hall measurement suggested the higher carrier concentration arose from incorporation of residual chlorine from the solution precursor during deposition into the films. The interstitially incorporated chlorine considerably influenced the electrical properties of the films.

Comparative Study of Non-Annealing and Annealing on Properties of ITO Deposited by RF Magnetron Sputtering

A comparison of the properties for two ITO thin films was performed. The two films were as follows – as-deposited and annealed ITO films. The influence of annealing on the structural, morphological, electrical, and optical properties was studied. The post-annealing treatment was done at a temperature of 400 for 1 h in air. The ITO thin films were deposited onto glass substrates by RF magnetron sputtering of a ceramic In2O3: SnO2 target in pure argon atmosphere at a low base pressure of <10-6 mbar and a RF power of 50 W. The films were characterized by XRD, FTIR, contact angle measurements, FE-SEM combined with EDX, Hall-effect measurements and UV-Vis transmission spectroscopy. The ITO films showed a crystalline structure with a predominant orientation (400) and its intensity was increased after the film was annealed. The structure of the annealed film became reformed in more perfect columnar structure. The annealed film showed a decrease in contact angle and increase in FTIR spectra intensity. The annealing induced more tin incorporated into the film from 0.51 to 2.62 at%. The resistivity decreased from 2.7x10-3 to 1.1x10-3 Ω cm with increasing mobility from 7.5 to 27.5 cm2 V-1 s-1 but decreasing carrier concentration from 3.0x1020 to 2.0 x 1020 cm-3. The optical band gap increased from 3.43 to 3.50 eV. All films showed highly transparency (∼85%) in the visible light region. Compared with the non-annealed ITO film, the air-annealed ITO film revealed the better properties except for carrier concentration.

High temperature thermoelectric properties of delafossite CuBO 2

CuBO₂ is prepared by a solid-state reaction method to investigate thermoelectric properties in high temperature. The XRD result confirms the CuBO₂ compound existing in this method. The Seebeck reveals the compound displays p-type thermoelectric material. The experimental results of electrical resistivity exhibited results of 0.004 S/cm to 0.038 S/cm with the temperature range of 650 to 830 K. The Seebeck value is in the range of 450 μV/K to 950 μV/K, and the thermal conductivity is in the range of 1.4 × 10^-5 to 5.3 × 10^-5 W/m-K² with the same temperature. The maximum PF and ZT is 5.3 × 10^-5 W/m-K² and 0.0016, respectively, at 960 K. This work demonstrates that the CuBO₂ delafossite-oxide compound displays the p-type thermoelectric materials.

Alcohol sensing of p-type CuFeO2 delafossite oxide

The sample of CuFeO2 delafossite was synthesized by solid state reaction for studying alcohol gas sensing properties. The Seebeck coefficient and electrical conductivity were measured in the high temperature ranging from 300 to 960 K. The CuFeO2 gas sensing displays high sensitive to ethyl alcohol gas in sensitivity ranging from 70 to 93 % and responding in 2 to 4 minute. The electronic characterization on the sample exhibits p-type conductor and displays electrical conductivity ranging from 3 to 13 S/cm with activation energy in 49 meV. This study suggests that CuFeO2 delafossite is a new one to be candidate in oxide material for alcohol gas sensing.

Nitrogen Concentrations on Structural and Optical Properties of Aluminum Nitride Films Deposited by Reactive RF-Magnetron Sputtering

We have fabricated Aluminum Nitride (AlN) films on the quartz substrates using RF-reactive magnetron sputtering method. The conditions of the films have been performed under different concentration ratios between nitrogen and argon. We have found that all obtained films were transparent in visible wavelength. By using X-ray diffraction (XRD) technique, it was found that the (002), (102) and (103) orientations were shown in XRD patterns. The (002) orientation was dominant when nitrogen concentration (CN) was at 40%. On the other hand, the refractive index and optical band gap energy of the films were determined as a function of CN. We have found that the refractive index weakly depended on CN, while optical band gap energy did not.

Structure and Piezoelectric Properties of Aluminum Nitride Thin Films on Quartz Substrates Deposited by Reactive RF-Magnetron Sputtering

This paper presents the effect of nitrogen concentration (CN) on aluminum-nitride bonding formation, structure and morphology of the aluminum nitride films. The films on the unheated substrates were deposited by radio frequency reactive magnetron sputtering technology using an aluminum target under argon/nitrogen mixture atmosphere. The FTIR and Raman spectra of the films confirmed their absorption bands corresponding to E1 (TO), A1 (TO), and E2 (high) vibration modes of the infrared active aluminum-nitride bonding. The crystallographic orientation of the films was optimized under CN of 40%. The cross-sectional FE-SEM image of the film under this condition showed the columnar structure. The dense columnar grains were uniformly observed on the films surface under all CN, except for CN of 20%. The bulk resistivity and piezoelectric property were investigated via the metal-insulator-metal structures. The results showed that the resistivity was in a range of 1014-1015 Ωcm while the effective piezoelectric coefficient was 11.03 pm/V.