UCLA

The goal of this dissertation is to develop a better understanding of the large field behavior and field induced phase transformations in relaxor ferroelectric single crystals. Development of relaxor ferroelectric single crystals requires experimental characterization of the thermo-electro-mechanical behavior to determine the linear coefficients as a function of stress, electric field, and temperature, and the limitations on linear behavior imposed by field driven phase transformations. The characterization of the large field behavior including dielectric loss, material coefficients, non-linear field induced phase transformations, and the mechanical, electrical, and thermal thresholds for linear behavior are discussed in detail. The full characterization of many compositions of [001]C and [011]C cut and poled single crystal lead indium niobate - lead magnesium niobate - lead titanate, xPb(In1/2Nb1/2)O3-(1-x-y)Pb(Mg1/3Nb2/3)O3-yPbTiO3 (PIN-PMN-PT), is presented and the effect of composition on the field induced phase transformation is discussed. PIN-PMN-PT with low PT concentrations was found to have a distributed phase transformation over a range of applied fields while PIN-PMN-PT with higher PT concentrations had discontinuous phase transformation behavior. Increasing the PT concentration or decreasing the PIN concentration increased the material coefficients but decreased the transformation threshold. A new approach to characterizing the large field behavior of relaxor ferroelectric single crystals was developed based on a combination of a work-energy based model of the driving forces for the phase transformation together with electric field loading while monitoring strain and electric displacement, and a measurement of mechanical compliance. The model was verified using the results from experimental characterization of PIN-PMN-PT and was found to accurately simulate the phase transformation behavior under combined mechanical, electrical, and thermal loads.