Glass-Glass Transitions by Means of an Acceptor-Donor Percolating Electric-Dipole Network

© 2017 American Physical Society. We report the ferroelectric glass-glass transitions in KN(K+/Nb5+)-doped BaTiO3 ferroelectric ceramics, which have been proved by x-ray diffraction profile and Raman spectra data. The formation of glass-glass transitions can be attributed to the existence of cubic (C)-tetragonal (T)-orthorhombic (O)-rhombohedral (R) ferroelectric transitions in short-range order. These abnormal glass-glass transitions can perform very small thermal hysteresis (approximately 1.0 K) with a large dielectric constant (approximately 3000), small remanent polarization Pr, and relative high maximum polarization Pm remaining over a wide temperature range (220-350 K) under an electrical stimulus, indicating the potential applications in dielectric recoverable energy-storage devices with high thermal reliability. Further phase field simulations suggest that these glass-glass transitions are induced by the formation of a percolating electric defect-dipole network (PEDN). This proper PEDN breaks the long-range ordered ferroelectric domain pattern and results in the local phase transitions at the nanoscale. Our work may further stimulate the fundamental physical theory and accelerate the development of dielectric energy-storing devices.