Piotr Jasinski

Nanocrystalline undoped ceria oxygen sensor

Abstract The results of a study of the structure and the electrical properties of nanocrystalline cerium oxide sensor are presented. The relationship between the resistance of the thin film ceria and oxygen partial pressure is shown. In the range of oxygen concentration from 10xa0ppm to 100% the conductivity of the ceria follows ( P O 2 ) −1/4 behavior. The response time of the sensor and its cross-sensitivity to nitrogen dioxide and sulfur dioxide is investigated.

Performance of a Porous Electrolyte in Single-Chamber SOFCs

A cell which consists of a porous 18 μm thick Y-doped ZrO 2 (YSZ) electrolyte (23 ′ 3 vol % open porosity) on a NiO-YSZ anode substrate and a cathode using (La, Sr)(Co, Fe)O 3 has been investigated in the single-chamber configuration. The cell performance and catalytic activity of the anode was measured in a flowing air-methane gas mixture with various flow rates. The results showed that the open-circuit voltage and the power density increased as the gas flow rate increased. The cell generated an open-circuit voltage of about 0.78 V, which was only about 0.1 V lower than that observed with dense electrolyte specimens. A maximum power density of 660 mW cm - 2 (0.44 V) was obtained at set temperature = 606°C (cell temperature = 744°C) in the flow rate of 900 cm 3 min - 1 , where the current efficiency was about 5% determined from fuel consumption.

Impedance Studies of Diffusion Phenomena and Ionic and Electronic Conductivity of Cerium Oxide

In this study, the electrical conductivity of undoped cerium oxide is evaluated using impedance spectroscopy. We have observed a new phenomenon, which is not related to electrode response but probably to diffusion processes in the grain boundary. An equivalent circuit has been constructed based on the observation, and the electronic bulk, ionic grain, and ionic grain boundary conductivities are calculated. Evaluation of fitting results to the proposed equivalent circuit suggests that diffusion-related phenomena are caused by blocking effects in the grain boundaries due to impurity segregation. Investigation of the grain boundary composition by energy dispersive X-ray spectroscopy shows that it contains detectable amounts of impurities in comparison to the grain, which supports the suitability of the proposed equivalent circuit.

Single Chamber Electrolyte Supported SOFC Module

An electrolyte supported single chamber solid oxide fuel cell (SOFC) module consisting of two cells has been proposed. The module consists of one Sm-doped CeO 2 (SDC) electrolyte substrate (0.5 mm thick with the size of 5× 10 mm), two Ni-SDC anodes on one side, and two SDC-(La,Sr)(Co,Fe)O 3 cathodes on the other side. Two modules with different electrode areas were prepared and tested using an air-propane mixture. The electrode area had a strong influence on the performance of the module. It was shown that the two-cell module generated 1.5 V open-circuit voltage and about 17 mW maximum power at 550°C.

Electrical Properties of YSZ Films Prepared by Net Shape Technology

The preparation of dense electrolyte films for most electrochemical devices is a crucial technological process. Net shape technology is a new approach, which uses a combination of colloidal suspensions and polymer precursor techniques, to obtain the dense electrolyte layers. It allows the overlapping of the thickness range from 1 to 10 mm in which other preparation techniques experience difficulties. Net shape processing is a low-temperature technology ~preparation temperature can be as low as 400°C! and it eliminates shrinkage of the film during the densification stage, so chemical reactions between the substrate and the film can be minimized. In this study two types of dense substrates were used to confirm these features of the net shape technology: single-crystal sapphire and platinum foil. It was shown that dense yttria-stabilized zirconia ~YSZ! layers can be obtained on both types of substrates at temperatures as low as 400°C. Moreover, further higher annealing temperature does not produce either shrinkage or cracking of the film. Electrical properties of YSZ films were measured in plane~on sapphire! and through the film~on platinum! using impedance spectroscopy and two-probe dc methods.

Impedance spectroscopy of BaTiO3 cubes suspended in lossy liquids as a physical model of two-phase system

Impedance spectroscopy techniques were used for analysis of the physical model in a two-phase system toward determining of dielectric constant of dielectric particles suspended in liquids at various solids loading (volume fraction) levels. Model experimental studies were conducted using BaTiO3 as a dielectric material that was prepared as small cubes of uniform size (2×2×1u2002mm). Barium titanate (BT) cubes having a dielectric constant of 3850 were immersed in liquids of low dielectric constant and moderate electrical conductivity. Measured impedance spectra consisted of two semicircles, which were fitted for (R∥C)(R∥C) equivalent circuit. The parameters obtained from fitting were compared with the data acquired from simulations of brick layer models and Maxwell–Wagner effective media model. In the investigated range of volume fractions the Maxwell–Wagner model correlates well with the data extracted from measurements.

Optical and electrical properties of Pr0.8Sr0.2MnO3 thin films

The results of studies on the preparation, structure, optical, and electrical properties of Pr0.8Sr0.2MnO3 thin films were presented. Dense films with a thickness of 50–70 nm were produced on monocrystalline sapphire substrates using a polymeric precursor spin coating technique. The results of the optical measurements were correlated with the annealing temperatures of the films and showed that the shape of the optical spectra changed as the structure changed from an amorphous to crystalline structure. The optical spectra was also used to determine the energy dependence of the absorption coefficient. The electrical conductivity was observed to be about three orders of magnitude higher for specimens which were crystalline as compared to amorphous.

Metal Supported Solid Oxide Fuel Cells - Selected Aspects

Metal supported solid oxide fuel cells are regarded as next generation fuel cells. In this configuration, the use of stainless steel allows lowering the cost of fuel cell fabrication and provides improvement in durability. Recent research progress brings promising results but many issues still must be overcome. In this paper some research insight into the description of properties of porous substrates and fabrication issues of porous metal supported fuel cells are highlighted.

A Novel Technology of Solid Oxide Fuel Cell Fabrication

Piotr Jasinski1, Toshio Suzuki2, Vladimir Petrovsky3, and Harlan U. Anderson3 1Gdansk University of Technology, Faculty of Electronics, Telecommunication and Informatics, ul. Narutowicza 11/12, Gdansk 80-952, Poland, 2National Institute of Advanced Industrial Science and Technology, AMRI, 2266-98 Anagahora Shimo-Shidami, 463-8560 Nagoya, Japan, 3University of Missouri Rolla, Electronic Materials Applied Research Center, 303 MRC, 65409 Rolla, USA