This work describes a method for measurement of R-curve behavior in ferroelectric ceramics using four point bending specimens with a controlled surface crack. A short surface crack is produced by a Knoop indentation and the damage zone is polished away. The results are compared for two compositions of lead lanthanum zirconate titanate (PLZT), an elastio-plastic ferroelectric composition and a linear elastic electrostrictive composition. R-curves are measured in the crack length regime of 0.1 to 0.8 mm. The ferroelastic composition displays a toughness increase from 0.7 to 1.4 MPam. The linear elastic composition displays a constant toughness of between 0.6 and 0.7 MPa√m. The R-curve behavior of PLZT 8/65/35 is attributed to ferroelastic toughening.

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