Ferroelastic switching and elastic nonlinearity in < 001 >-oriented Pb(Mg1/3Nb2/3)O-3-PbTiO3 and Pb(Zn1/3Nb2/3)O-3-PbTiO3 crystals

The strain versus electric field (epsilon-E) and strain versus stress (epsi lon-sigma) response characteristics of < 001 >-oriented crystals of Pb(BI1/ 3BII2/3)O-3-PbTiO3 have been investigated. Under zero field, a ferroelastic switching has been observed under moderate uniaxial prestress levels. The magnitude of the elastic strain switched was similar to 0.4%. In addition, an elastic softening was observed during switching, where the elastic const ant decreased from similar to 10(10) to similar to 3x10(9) N/m(2). At highe r stresses, the elastic constant stiffened to similar to 5x10(10) N/m(2), w hich upon application of dc electrical bias softened to similar to 10(10) N /m(2). The importance of ferroelastic switching and elastic nonlinearity is discussed. (C) 2000 American Institute of Physics. [S0021-8979(00)01121-X] .