The strength of PIN-PMN-PT single crystals under bending with a longitudinal electric field

The effect of an electric field on the bending behavior of [001] oriented and poled relaxor Pb(In_1/2Nb_1/2)O₃-Pb(Mg _1/3Nb_2/3)O₃-PbTiO₃ (PIN-PMN-PT) single crystals was measured using a four point bending apparatus with a longitudinal electric field applied to the bar during bending. The surface finish and electric field amplitude were observed to affect the bending strength. Polished surfaces improve the tensile strength, while also polishing the edges resulted in a significantly larger increase in strength. Application of a DC electric field in the polarization direction during the tests reduced the strength. The four point bending apparatus also produces both tensile and compressive stress-strain curves for the material. Uniaxial compressive loading with an electric field in the [001] direction was carried out to compare the stress versus strain behavior measured in bending with that measured in uniaxial compression. Although the uniaxial compression behavior displays effects of a rhombohedral to orthorhombic phase transformation, this behavior is not observed on the compressive side in the bend bars.