Influence of CeO₂ Reduction on the Microstructure and Mechanical Properties of Pulsed Electric Current Sintered Y₂O₃–CeO₂ Co‐Stabilized ZrO₂ Ceramics

Abstract

The combination of yttria co‐stabilization and pulsed electric current sintering allowed full densification of CeO2‐containing ZrO2 ceramics in a graphite environment, while avoiding spontaneous catastrophic material degradation due to ceria reduction. Tetragonal ZrO2 ceramics were obtained by pulsed electric current sintering (PECS) of 1 mol% Y2O3+6 mol% CeO2 (1Y6Ce) stabilizer‐coated monoclinic ZrO2 powder with 2 wt% Al2O3 as sintering additive for 2 min at 1450° or 1550°C under a maximum pressure of 60 MPa. In addition, a 2 mol% Y2O3 doped ZrO2 (2Y) ceramic was used as reference material to elucidate the effect of CeO2 reduction in the densified 1Y6Ce ceramics. The influence of the CeO2 reduction and sintering temperature on the microstructure and mechanical properties of the co‐stabilized ZrO2 ceramics was investigated. A graded microstructure with a gradient in color and mechanical properties were observed in the 1Y6Ce ceramic sintered at 1450°C, whereas the 1Y6Ce ZrO2 sintered at 1550°C and the 2Y ceramic had a uniform color and mechanical properties. Additionally, the formation of an elongated CeAl11O18 (Ce2O3·11Al2O3) phase was observed in the 1Y6Ce ceramic sintered at 1550°C. The formation of the graded color, the presence of the CeAl11O18 phase, as well as the graded fracture toughness profile were explained in terms of the gradual reduction of CeO2 to Ce2O3 in the 1Y6Ce ceramic.

The relationship between microstructure and fracture toughness of zirconia toughened alumina (ZTA) added with MgO and CeO2

“…The addition of CeO 2 also decreases the monoclinic phase, as shown at 28°and 32°Bragg angles. Previous work done by Huang et al, who studied the reduction of CeO 2 in ZrO 2 ceramics, also shows a reduction of the monoclinic phase with the addition of CeO 2 [20]. The reduction of the monoclinic phase in ZTA-MgO-CeO 2 system increases the overall toughness of the ceramic composite.…”

Effect of calcia co-doping on ceria-stabilized zirconia

“…The change in colour could be attributed to a partial ceria reduction during the sintering process due to a lack of oxygen supply, as different colorations have been reported in literature when sintering Ce-TZP ceramics in different atmospheres and in reduced partial oxygen pressure. This effect seems to be related to the production of vacancies due to an oxygen deficiency [48]- [56]. Thus, it seems that ceria-stabilized zirconia ceramics are very sensitive to the oxygen supply in the furnace during 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 sintering, being able to reduce even in air in small conventional sintering furnaces, typically resulting in a colour gradient with a darker bulk and a brighter surface.…”

Microstructure and Mechanical Properties of ZrB2‐Based Composites Reinforced and Toughened by Zirconia

“…1. Apparently, the phase analysis indicates the predominant phases for the initial mixed powders, at the range of 2θ: 27°–35°, 15 are ZrB 2 , t ‐ZrO 2 , and some m ‐ZrO 2 . However, too much of m ‐ZrO 2 phase has not been detected in the hot‐pressed composite by comparing the two figures.…”