Effect of GeO<SUB>2</SUB> and NdO<SUB>1.5</SUB> Co-doping on High-temperature Ductility in TZP

Abstract

Superplastic flow behavior in 1 mol% of GeO2 and 1 mol% of NdO1.5 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 NdO1.5-doping slightly enhances high-temperature ductility in 3Y-TZP, but 1 mol% of GeO2 and 1 mol% of NdO1.5 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 NdO1.5 co-doped TZP is larger than that in GeO2 or NdO1.5 singly doped TZP. The reduction in the flow stress due to GeO2 and NdO1.5 co-doping is probably related to the increment in the segregation width.