Comportamiento eléctrico de películas de CeO2 ante O2 y CO

FEDERICO SCHIPONI; ANDREA PRADO; JAZMIN CALVECHE; CARLOS MACHI; JORGE PÁEZ RODRIGUEZ; MIGUEL PONCE

Santa Fe

Congreso; Congreso Internacional de Metalurgia y Materiales 14° SAM-CONAMET / IBEROMAT 2014; 2014

Asociación Argentina de Materiales / Sociedad Chilena de Metalurgia y Materiales

CeO2 has relevant physical and chemical properties that have found application in different fields, like catalysis, photocatalysis, and medicine, and particularly in membranes and fuel cells. The activity of CeO2 has been explained on the basis of its ability to store and transport oxygen, which is caused by the change in the oxidation state of cerium ions (from Ce3+to Ce4+). Due to its chemical stability and high diffusion coefficient for oxygen vacancies, CeO2 has been well established as an oxygen sensor. Cerium oxide was obtained by the polimeric precursor method (Pechini) and using as a precursor penta-hydrated cerium nitrate. We put special attention to the pH value in the synthesis. The most suitable process for the obtention of CeO2 nanoparticles is to perform pre-dissolution precursors in water and bring the mixture to an acidic pH of 2. In this work we analyze the cerium oxide response to oxygen and CO. The electrical resistance and capacitance was also studied. The sensitivity (S) was studied as a function of the temperature in order to find its maximum value. For our studies, thick, porous film samples were made by painting onto insulating alumina substrates on which electrodes with an interdigitated shape were deposited by sputtering. After painting the samples, they were thermally treated up to 380 °C and exposed to an air atmosphere at 380°C during 1 hour. The surface microstructure was characterized using X-ray diffraction and transmission electron microscopy and the substrates were studied with a profilometer. Finally, the electrical conduction mechanisms were theoretically modeled. In the modeling the oxygen in-out diffusion was considered.