Thermotropic Phase Boundaries in Classic Ferroelectrics
Novel monoclinic subphases in ferroelectric BaTiO3 were observed by Center for Nanoscale Materials users from The Pennsylvania State University in collaboration with CNM's X-Ray Microscopy Group and scientists from the Center for Nanophase Materials Sciences. The newly discovered low-symmetry intermediate phases are found to be locally stabilized near thermotropic phase boundaries in simple ferroelectrics, and they exhibit large enhancements in nonlinear optical and piezoelectric ;property coefficients. The findings reveal that phase transitions in ferroelectrics are intimately coupled to the underlying domain microstructure. Nanoscale scanning X-ray diffraction measurements harnessing the unique structural sensitivity of the CNM Hard X-Ray Nanoprobe unambiguously demonstrated the intrinsic monoclinic nature of the subphase. The discovery presents unique opportunities for the design of "green" high-performance nanoscale energy materials.