2022, Vol. 26 ›› Issue (27): 4320-4324

Effect of grain boundary segregation on low-temperature aging of 3% yttrium oxide stabilized zirconia ceramics co-doped with GeO2 and TiO2

Zhou Zhiwei1, Niu Wanqiong1, Ren Lijuan1, Wang Zhenhua1, 2   

Abstract: BACKGROUND: Many recent studies have found that zirconia co-doped with TiO2 and GeO2 exhibits excellent superplasticity.
OBJECTIVE: To investigate the improvement of anti-cryogenic aging properties of zirconia materials stabilized by 3% yttrium oxide co-doped with TiO2 and GeO2.
METHODS: The 3% yttrium oxide stabilized zirconia material samples co-doped with GeO2 and TiO2 were prepared by mechanical ball milling, drying, and pressure free sintering. Among them, the mole percentage of 3% yttrium oxide stabilized zirconia was 98%. The mole percentages of TiO2 powder (purity 99.8%) and GeO2 powder were 1.5% and 0.5%, respectively, which was recorded as the 1.5Ti-0.5Ge group. The mole percentages TiO2 powder (purity) 99.99%) and GeO2 powder were 1% and 1%, respectively, which was recorded as 1Ti-1Ge group. The mole percentages of TiO2 powder (purity 99.8%) and GeO2 powder were 0.5%, 1.5%, respectively, which was recorded as 0.5Ti- 1.5Ge group. The microstructure of all samples was investigated by scanning transmission electron microscopy and energy spectroscopy. After treatment in an autoclave, the conversion of all samples was measured by an X-ray diffractometer.
RESULTS AND CONCLUSION: (1) Scanning transmission electron microscopy results showed that the composite powders of a 3% yttrium oxide stabilized zirconia material co-doped with GeO2 and TiO2 had uniform particle size and were distributed over a 50 nm; the particle shape was basically spherical and well dispersed, but there was a small amount of agglomeration. X-ray diffractometer exhibited that the Ge4+, Ti4+ stabilizers could inhibit the low-temperature aging effect of zirconia materials. With the increase of the doping amount of GeO2, the low-temperature aging resistance of zirconia could be improved. Energy spectrometer detection demonstrated that with the increase of dopant content, the degree of grain boundary segregation increased, but even if the doping amount of Ge4+ was small, the degree of grain boundary segregation could be comparable to that of Ti4+ with a large amount of doping. (2) The results suggest that the addition of GeO2 and TiO2 improved 3% yttrium oxide stabilized zirconia ceramics against low-temperature aging properties. GeO2 is superior to TiO2 in resisting low-temperature aging and can be used as the first choice.
Key words: mechanical ball milling, grain boundary segregation, low-temperature aging resistance, germanium dioxide, titanium dioxide, zirconia, X-ray diffraction