Evaluation of response characteristics of resistive oxygen sensors based on porous cerium oxide thick film using pressure modulation method |
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| Affiliation: | 1. Département de Physique, Université de Liège, B-4000 Sart Tilman, Belgium;2. Physics department, Faculty of science, Fayoum University, 63514 Fayoum, Egypt;3. Low Temperature Physics and Superconductivity Department, Physics Faculty, M.V. Lomonosov Moscow State University, 119991 Moscow, Russia;4. Theoretical Physics and Applied Mathematics Department, Ural Federal University, 620002 Ekaterinburg, Russia;5. Institute of Experimental Mineralogy, Russian Academy of Sciences, Chernogolovka, Moscow 142432, Russia;6. INPAC - Institute for Nanoscale Physics and Chemistry, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium;1. Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada del Instituto Politécnico Nacional, Legaria # 694 Col. Irrigación, C.P. 11500 México D.F., Mexico;2. Departamento de Física Aplicada, CINVESTAV-IPN, Unidad Mérida, km. 6 Carretera Mérida-Progreso, C.P. 97310 Mérida, Yucatán, Mexico;3. Departamento de Física, CINVESTAV-IPN, Apartado Postal 14-740, 07000 México D.F., Mexico;4. Facultad de Física, Universidad de La Habana, San Lázaro y L, C.P. 10400, La Habana, Cuba;5. LANE, CINVESTAV-IPN, Apartado Postal 14-740, 07000 México D.F., Mexico |
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| Abstract: | In order to reduce the response time of resistive oxygen sensors using porous cerium oxide thick film, it is important to ascertain the factors controlling response. Pressure modulation method (PMM) was used to find the rate-limiting step of sensor response. This useful method measures the amplitude of sensor output (H(f)) for the sine wave modulation of oxygen partial pressure at constant frequency (f). In PMM, “break” response time, which is minimum period in which the sensor responds precisely, can be measured. Three points were examined: (1) simulated calculations of PMM were carried out using a model of porous thick film in which spherical particles are connected in a three-dimensional network; (2) sensor response speed was experimentally measured using PMM; and (3) the diffusion coefficient and surface reaction coefficient were estimated by comparison between experiment and calculation. The plot of log f versus log H(f) in the high f region was found to have a slope of approximately ?0.5 for both porous thick film and non-porous thin film, when the rate-limiting step was diffusion. Calculations showed the response time of porous thick film was 1/20 that of non-porous thin film when the grain diameter of the porous thick film was the same as the thickness of non-porous thin film. At 973 K, “break” response time (tb) of the resistive oxygen sensor was found by experiment to be 109 ms. It was concluded that the response of the resistive oxygen sensor prepared in this study was strongly controlled by diffusion at 923–1023 K, since the experiment revealed that the slope of plot of log f versus log H(f) in the high f region was approximately ?0.5. At 923–1023 K, the diffusion coefficient of oxygen vacancy in porous ceria (DV) was expressed as follows: DV (m2s?1) = 5.78 × 10?4 exp(?1.94 eV/kT). At 1023 K, the surface reaction coefficient (K) was found to exceed 10?4 m/s. |
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