Synthesis and Characterization of Zirconium Oxide Systems with Yttrium Rich Rare Earth Concentrate Additives

Abstract

In this work, the yttrium rich rare earth concentrate (Re2(CO3)3) was used as additive aiming stabilization of cubic an tetragonal phases at commercial zirconium oxide with 3% mol of yttrium oxide. The use of high purity rare earth oxide as additive is being commercially used and this work aims to demonstrate the potential use of lower cost additives to produce solid electrolyte for oxygen sensors and fuel cell applications. The powders for the additive production were synthesized by the controlled precipitation method. After synthesis, the powders were de-agglomerated using mechanical grinding and mixed to commercial zirconia to produce the compositions ZrO2:3% Mol Y2O3:ƞ % Mol Re2O3 (ƞ=3,4,5,6), followed by uniaxial press and sintering at 1500 0C in two hours. The obtained sintered densities were above 96% of theoretical. X-Ray diffractometric analysis and Rietweld refinement demonstrated the stabilization of cubic and tetragonal phases for all samples with yttrium rich rare earth concentrate additives. Finally the electric behavior of the evaluated samples was carried out with complex impedance spectroscopy, showing conductivity improvement for samples with the chosen additive. At 500 0C the sample A-9% had a conductivity of 1,11E-3Ω-1.cm-1, well above of the sample without additive with conductivity 5,88E-4Ω1.cm-1, indicative that use of yttrium rich rare earth concentrate as additive increases considerably the ionic conductivity of comercial zirconium oxide. Key words: rare earth concentrate, controlled precipitation, ionic conductivity