Y. Kubota et al., ELASTIC-MODULUS AND FRACTURE-TOUGHNESS OF CEO2-CONTAINING TETRAGONAL ZIRCONIA POLYCRYSTALS, Nippon Seramikkusu Kyokai gakujutsu ronbunshi, 102(2), 1994, pp. 175-179
The lattice constants, elastic modulus and fracture toughness of 12 mo
l% CeO2-containing tetragonal zirconia polycrystals with grain sizes o
f 2.8 mum (sintered at 1500-degrees-C, Z12C-I) and 6.1 mum (sintered a
t 1600-degrees-C, Z12C-PI) were measured. Lattice constants (a(t) and
c(t) axes) of tetragonal zirconia for Z12C-PI were larger than those f
or Z12C-I. On the other hand, the axial ratio ct/square-root 2 a(t) fo
r Z12C-PI was smaller than that for Z12C-I. Therefore, it was estimate
d that tetragonal zirconia in Z12C-PI was more stable than that in Z12
C-I. Young's modulus at room temperature was 194-195 GPa for both spec
imens. The effect of grain size on Young's modulus was not observed. T
he Young's modulus decreased with increasing temperature and was 179-1
80 GPa at 400-degrees-C. Fracture toughnesses at room temperature were
6.4 MPa.m1/2 for Z12C-I and 6.7 MPa.m1/2 for Z12C-PI. That is, fractu
re toughness with a large grain size was larger than that with a small
grain size. The fracture toughness decreased gradually with increasin
g temperature and was 4.0 MPa.m1/2 for Z12C-I and 4.2 MPa.m1/2 for Z12
C-PI at 300-degrees-C. The monoclinic zirconia content on the fracture
surface for Z12C-PI with large grain size was comparable to that for
Z12C-I with small grain size at room temperature. Fracture modes in Z1
2C-I was characterized by intergranular mode and that in Z12C-PI, by t
ransgranular mode. It is concluded that the fracture toughness for Z12
C-PI was larger than that for Z12C-I because of the difference in frac
ture modes.