Synthesis and characterization of nanometric yttrium-doped hafnia solid solutions

Nanometric-sized yttrium doped HfO2 powders were obtained by applying metathesis and combustion reactions. The tailored composition of solid solutions was: Hf1−xYxO2−δ with concentration “x” ranging from 0 to 0.2. HfCl4 was used as a source of hafnium whereas Y(NO3)3·6H2O was used as a source of yttrium. The obtained powders were annealed at different temperatures in order to induce crystallization of HfO2. The influence of dopant concentration, annealing temperature and annealing time on powder properties was examined. The XRD analysis revealed that the crystal structure of HfO2 depends on the dopant concentration. The samples doped with 20 mol% of yttrium and annealed at 1500 °C had high-temperature, cubic structure even after cooling to room temperature. The presence of relatively large amount of dopant was beneficial in stabilizing highly desirable cubic phase of HfO2. It was found that the crystallite size lies in the nanometric range (<10 nm).