Short crack R-curves in ferroelectric and electrostrictive PLZT

This work describes the measurement of R-curve behavior in ferroelectric ceramics using four-point bend specimens with controlled semielliptical surface cracks. The results are compared for two compositions of lead lanthanum zirconate titanate. One exhibits ferroelastic behavior, the other electrostrictive linear elastic behavior. R-curves are measured in the crack length regime of 0.1 to 0.8 mm, The ferroelastic composition displays a toughness increase from 0.5 to 1.2 MPa.m(1/2) The linear elastic composition displays a flat R-curve. The R-curve behavior is attributed to ferroelastic toughening.