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Solid solutions of ZrO2 and HfO2 are potential electrolyte materials for intermedi ate-temperature SOFC because both are oxy gen-ion conductors. The main challenge for these compounds is to reduce the relatively high value of the activation energies vacancies diffusion, which is influenced by several factors. In this work the thermal evolution of CaO-HfO2 materi als have been investigated. (CaO)y-Hf(l-y)O(2-y) (y = 0.06, 0.14 y 0.2) coatings and powders were synthesized by chemical solution deposition (CSD). Films were deposited onto alumina substrates by Dip Coating technique, the burning of organic waste was carried out at 500 °C under normal atmosphere and then the films were thermally treated at intervals of temperature rising to a maximum temperature of 1250 °C. By means Glazing Incidence X-ray Diffraction (cp-20 configuration) the phases were studied in the annealed films. On the other hand, the thermal evolution and crystallization process of powders were analyzed in-situ by HT-XRD. The phenomena crystallization occurred in films and powders were analyzed. The activation energies of diffusion of oxygen vacancies of HÍO2-14 mole% CaO and HÍO2-20 mole% CaO films were measured from the thermal evolution of the relaxation constant measured by Per turbed Angular Correlation Technique.

The hyperfine quadrupole interaction at Hf sites in films and powders of 14 mol% CaO-HfO 2 and 20 mol% CaO-HfO 2 has been determined as a function of temperature. Results indicate the formation of a cubic solid solution and other microstructures assigned to the φ 1 (CaHf 4 O 9 ) and φ 2 (Ca 6 Hf 19 O 44 ) phases. Dynamical effects on the electric field gradient reveal the existence of oxygen vacancies movements in the solid solution. The thermal behavior of the relaxation constant observed in films allowed the determination of activation energies of 0.54 eV and 0.70 eV for the 14 mol% and 20 mol% CaO doped hafnias, respectively. The influence of the microdomains and the stability of the cubic solid solution are discussed.

Se obtuvieron polvos del sistema Ytterbia-Circona (Yb 2 O 3-ZrO 2) con distintas concentraciones de dopante (8, 9 y 10% molar del óxido) a través de precursores líquidos utilizando Acetoin como agente quelante. Las transiciones de fase entre temperatura ambiente y 1300°C, se estudiaron mediante análisis térmico (DTA y TGA), y se estudió la microestructura final obtenida luego del tratamiento térmico, con técnicas de XRD en configuración -2. Se encontró que para las tres concentraciones de Yb 2 O 3 se consigue estabilizar la fase cúbica a temperatura ambiente, y la temperatura de cristalización es de 500ºC Palabras Claves: ZrO 2-Yb 2 O 3 , polvos, evolución de fases (Yb 2 O 3) x-Zr (1-2x) O 2-x (x: 0.08, 0.09 y 0.10) powders were synthesized by Chemical Solution Deposition (CSD) from alcoholic solution using 3-hidroxi-2-butanone (Acetoín) as a chelant agent. The elimination of organic species and phases evolution were studied by means of a thermal and gravimetric DTA/TG analysis in the range of RT-1300ºC. The final structure was observed in the powders by X-ray Diffraction (-2 configuration). The powder crystallizes at 500ºC. In the powder with content of Yb the fluorite-type cubic phase was retained at room temperature.

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