Borkar, Hitesh and Rao, Vaibhav and Dutta, Soma and Barvat, Arun and Pal, Prabir and Tomar, M. and Gupta, Vinay and Scott, J. F. and Kumar, Ashok (2016) Novel optically active lead-free relaxor ferroelectric (Ba0.6Bi0.2Li0.2)TiO3. Journal of Physics: Condensed Matter, 28 (26). ISSN 0953-8984

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We discovered a near-room-temperature lead-free relaxor-ferroelectric (Ba0.6Bi0.2Li0.2)TiO3 (BBLT) having A-site compositionally disordered ABO(3) perovskite structure. Microstructure-property relations revealed that the chemical inhomogeneities and development of local polar nano-regions (PNRs) are responsible for dielectric dispersion as a function of probe frequencies and temperatures. Rietveld analysis indicates mixed crystal structure with 80% tetragonal structure (space group P4mm) and 20% orthorhombic structure (space group Amm2), which is confirmed by the high resolution transmission electron diffraction (HRTEM). Dielectric constant and tangent loss dispersion with and without illumination of light obey nonlinear Vogel-Fulcher (VF) relations. The material shows slim polarization-hysteresis (P-E) loops and excellent displacement coefficients (d(33) similar to 233 pm V-1) near room temperature, which gradually diminish near the maximum dielectric dispersion temperature (T-m). The underlying physics for light-sensitive dielectric dispersion was probed by x-ray photon spectroscopy (XPS), which strongly suggests that mixed valence of bismuth ions, especially Bi5+ ions, comprise most of the optically active centers. Ultraviolet photoemission measurements showed most of the Ti ions are in 4 + states and sit at the centers of the TiO6 octahedra; along with asymmetric hybridization between O 2p and Bi 6s orbitals, this appears to be the main driving force for net polarization. This BBLT material may open a new path for environmental friendly lead-free relaxor-ferroelectric research.

Item Type: Article
Additional Information: Copyright for this article belongs to M/s IOP Publishing.
Subjects: Applied Physics/Condensed Matter
Depositing User: Dr. Rajpal Walke
Date Deposited: 07 Mar 2018 11:00
Last Modified: 07 Mar 2018 11:00

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