Oxide Laminates with High Strength and Work-of-Fracture

ABSTRACTSix types of oxide laminates consisting of combinations of xenotime (YPO4) with zirconia (ZrO2), monazite (LaPO4) with ZrO2, and aluminum orthophosphate (AlPO4) with alumina (Al2O3) were studied. They were fabricated by repeatedly stacking two or three kinds of tape-cast layers, lamination, organic burnout and consolidation by hot-pressing. Two of the YPO4-containing ZrO2 laminates were stacked in a YPO4/yttria-stabilized ZrO2 (Y-ZrO2)/30 vol% Y-ZrO2-70 vol% Al2O3(YZ3-A7)/Y-ZrO2 sequence and in a YPO4/Y-ZrO2 sequence. High strength (∼360 MPa) and apparent work-of-fracture (WOF = ∼ 8.2 kJ/m2) were measured in the first laminate. This oxide laminate demonstrates high damage-tolerance without loss of strength. Both properties were comparable with those of non-oxide laminates. There was an approximately 200-fold increase in WOF, as compared with pure Al2O3. A toughening mechanism by means of the residual, interlaminar shear stress-enhanced, interface delamination is proposed for these good results. Two of the LaP04-containing ZrO2 laminates were fabricated in a LaPO4/70 vol% doped ZrO2-30 vol% Al2O3 stacking sequence and in a LaPO4/Y-ZrO2 sequence. Another two of the AlPO4-containing Al2O3 laminates are fabricated in an AlPO4/Al2O3 and in a (50 vol% AlPO4-50 vol% Al2O3)/Al2O3 stacking sequence. The fracture behavior of these multilayered laminates was also studied. The different results among the three kinds of laminates are discussed.