Effect of GeO₂ and NdO_1.5 Co-doping on High-temperature Ductility in TZP

Abstract

Superplastic flow behavior in 1 mol% of GeO₂ and 1 mol% of NdO_1.5 co-doped ZrO₂-3 mol%Y₂O₃ (3Y-TZP) was examined at 1400°C under an initial strain rate of 1 × 10⁻⁴ s⁻¹. 1 mol% of GeO₂ or NdO_1.5-doping slightly enhances high-temperature ductility in 3Y-TZP, but 1 mol% of GeO₂ and 1 mol% of NdO_1.5 co-doped TZP exhibits large elongation to failure of more than 600% at 1400°C. The large ductility in TZP due to Ge⁴⁺ and Nd³⁺ co-doping can be explained from reduction in the flow stress. High-resolution electron microscopy (HREM) and energy-dispersive X-ray spectrometer (EDS) analysis revealed that Y³⁺, Ge⁴⁺ and Nd³⁺ cations segregate in the vicinity of grain boundaries in the present materials. The segregation width of the dopant cation across the grain boundaries in GeO₂ and NdO_1.5 co-doped TZP is larger than that in GeO₂ or NdO_1.5 singly doped TZP. The reduction in the flow stress due to GeO₂ and NdO_1.5 co-doping is probably related to the increment in the segregation width.