Tungsten bronze ferroelectrics with a morphotropic phase boundary (MPB) have become increasingly important for a variety of applications because of their enhanced and unique properties near the MPB. Lead barium niobate (Pb1-xBaxNb2O6) crystals, which have a morphotropic phase boundary between the orthorhombic (1 - x > ∼0.63) and tetragonal (1 - x < ∼0.63) phases, were grown in sealed Pt crucibles by the vertical Bridgman method for tetragonal compositions near the MPB, and their ferroelectric properties were investigated. The ferroelectric domain structures in as-grown crystals were revealed either by etching in hydrofluoric acid or by polishing with colloidal silica, the latter providing clearer features. Domain size on the surface perpendicular to the polar axis was 10-50 μm. Crystals could be poled by slowly cooling from above the Curie temperatures (300-400°C) under a dc field of 5 V/mm. The spontaneous polarization Ps of tetragonal Pb1-xBaxNb2O6 was found to be in the range of 0.40-0.70 μmC/mm2 at room temperature depending on composition and increased as the composition approached morphotropic phase boundary (1 - x = ∼0.63), as expected.
Bibliographical noteFunding Information:
This research was funded by the Defense Advanced Research Projects Agency (DARPA) through the Photorefractive Information Storage Materials (PRISM) Program and through the Center for Nonlinear Optical Materials (CNOM) at Stanford University. Facilities support was provided by the NSF/MRSEC Program through the Center for Materials Research at Stanford University. The authors wish to thank Greg Miller in Ginzton Laboratory, Stanford University for his discussions and helps with the poling experiments.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics
- Mechanics of Materials
- Mechanical Engineering