Phase equilibria of zirconia-dispersed ceramic in NiOAl2O3ZrO2 system

✍ Scribed by W.S. Chang; S. Chen; P. Shen

• Publisher: Elsevier Science
• Year: 1991
• Tongue: English
• Weight: 658 KB
• Volume: 145
• Category: Article
• ISSN: 0921-5093
• DOI: 10.1016/0921-5093(91)90301-3

✦ Synopsis

Powders of NiO, AI203 and ZrO~ mixed in various ratios were sintered between 1200 and 1600 °C and their phase equilibria studied by X-ray diffraction and electron microscopy. Partially stabilized ZrO, (PSZ) consisting of tetragonal ZrO 2 (t-ZrO2) precipitated in the cubic ZrO 2 (c-ZrO2) matrix was not formed because the solubility of NiO and/or AI20~ in ZrO2 was not enough to stabilize the c-ZrO2 phase. Instead, t-ZrO2 particles were constrained in the matrix phase of NiO and/or spinel which was formed by reacting NiO with AI20> At 1600 °C, t-ZrO2 equilibrated with the stoichiometric NiAI204 spinel when free NiO was present, with spinel of varied nickel-to-aluminium stoichiometry when Al203 content exceeded NiO, and with Al203-rich spinel and free AI~O3 (corundum) when AI20~ was saturated in spinel. The implications of these results to TBCs are discussed.