| The residual stresses of indentation on Pb(Zr0.52Ti0.48)O3(PZT) were tested by double indentations experiments. Poling effects on fracture toughness of PZT were studied. The mechanics of anisotropy of poled PZT is analyses. The effect of grain fining on fracture toughness of PZT was discussed. It is concluded that it is caused by domain transformation that residual stress of indentation crack along poling direction is lowest in all directions. The mechanics that fracture toughness of poled PZT is anisotropic is proposed.The effect of poling on strength of PZT was researched by R-curve. It is concluded that the ascending R-curve of poling direction of PZT was determined because of domain transformation trip. The relation between strength and crack depth in poling direction is changed by ascending R-curve, and the ability of bearing crack in poling direction is enhanced.The relation between indentation fracture toughness and indentation load was studied by series load experiment, and the relation between series fracture toughness at various load and R-curve was discussed. It is concluded that with load of indentation experiment increasing, the apparent fracture of poling direction is improved because of domain transformation. The fracture toughness of other direction has nothing with indentation load. The indentation experiment could be used for R-cure test method.Finally, the relation between fracture pattern of PZT and fracture toughness was discussed by fractal geometry, and the effect of grain fining on fracture toughness was researched. It is concluded that the fractal dimension of ceramic fracture pattern has direct proportion with fracture toughness. The fractal dimension of PZT with finer grain is bigger than normal PZT , so is the fracture toughness.
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