The role of processing variables in the flux growth of lead zinc niobate-lead titanate relaxor ferroelectric single crystals

Relaxor ferroelectric single crystals of Pb(Zn_1/3Nb_2/3)O₃-PbTiO₃ (PZN-PT) are of interest as high performance transducers due to their very large piezoelectric coupling and dielectric properties. A high temperature flux solution method was used to grow (1 - x)PZN-(x)PT, where x = 0.0, 0.1 and 0.15 single crystals. Processing conditions were optimized to increase the size and yield of the perovskite crystals, including variation of the flux to composition ratio, cooling rate, soak time and soak temperature. The crystals varied in size from 0.01 cm to 1.5cm on an edge, and in color from opaque to brown due to the changes in processing conditions. The crystals were characterized by XRD, dielectric constant and dielectric loss measurements. As the content of PT increased the transition from the paraelectric to the ferroelectric phase approached first order behavior and the crystal structure transformed from rhombohedral to tetragonal. This structure transition caused the lattice constant along the c-axis to elongate as the c/a ratio increased. At room temperature, the dielectric constants for the PZN-PT compositions along the [111] or [001] axes were as great as 5000 and the dielectric losses were as low as 0.01.