YSZ nanoparticles and thin films prepared in a single crystallization step at low temperature

Yttria Stabilized Zirconia (YSZ) are among the most versatile materials of the modern age, but their preparation requires high temperatures and several crystallization steps. Here we report how YSZ nanoparticulated powders and thin films have been obtained in a single crystallization step at lower temperatures than others reported before. Solid precursors with different molar ratios between ammonium nitrate and Zr-Y-citrate were studied to approach an optimal fuel/oxidizer ratio that guarantees a complete autocombustion of the precursor, so that cubic 10.5% mol YSZ nanoparticles are synthetized in one step at 400 °C. A solid precursor optimized as described before was employed for the fabrication of dense and granular YSZ thin films combining, for the first time, the Ultrasonic Spray Pyrolysis with an autocombustion reaction. The samples were structurally, thermally, morphologically, optically and electrically characterized. The cubic 10.5% mol YSZ nanoparticles exhibit an ionic conductivity close to 0.2 S cm^-1 at 620 °C. The cubic 12.5% mol YSZ phase predominates in the micrometric particles agglomerates observed in the granular film, where the impedance response was very resistive. Nanoparticles of 7.5% mol YSZ with a two-phase mixture (tetragonal/cubic) predominate in the dense film. In this film refractive index as high as 1.98 and conductivity around 0.1 S cm^-1 at 600 °C were measured. These results are promissory for applications at low temperatures.