Hyperfine interactions in ZrO2–5 wt.% Al2O3 ceramics

Two powder samples of ZrO₂-5 wt.% Al₂O₃ derived from precursor solutions of different pH – 2 for sample (C) and 4 for sample (D) – were prepared by the precipitation method. They were studied using PAC between RT and 1150oC and XRD after heating at increasing temperatures. According to XRD, the addition of Al₂O₃ causes the complete stabilization of tetragonal zirconia in both samples. At a nanoscopic level, however, they present different interactions and thermal evolutions. Sample (C) exhibits predominantly the t₁- and dynamic t₂-forms already reported for pure and yttria-doped stabilized tetragonal zirconias. On the other hand, sample (D) exhibits a novel nanoconfiguration depicted by a totally asymmetric and dynamic EFG whose population achieves 86% at 1150oC and which has been associated to aluminium solubility in zirconia. Upon cooling gradually to RT from the highest temperature, (C) transforms completely to m-ZrO₂ and (D) remains 65% in the metastable tetragonal phase. This revised version was published online in August 2006 with corrections to the Cover Date.