We have reported the structural, thermal, microscopic, magnetization, polarization, and dielectric properties of BiFeO 3 ceramics synthesized by a rapid liquid-phase sintering technique. Optimum conditions for the synthesis of single-phase BiFeO 3 ceramics were obtained. Temperature-dependent magnetization and hysteresis loops indicate antiferromagnetic behavior in BiFeO 3 at room temperature. Although saturated ferroelectric hysteresis loops were observed in single-phase BiFeO 3 ceramic synthesized at 880°C, the reduced polarization is found to be due to the high loss and low dielectric permittivity of the ceramic, which is caused by higher leakage current.

In the present work, we performed electrochemical measurements to investigate Li (de)intercalation behavior and Raman spectroscopic studies to understand structural changes during charge−discharge processes and verify the structural stability after electrochemical cycling of the AlPO 4 -coated Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 composite cathode. Physicochemical characterization techniques confirmed the well-crystalline layered composite nature of the prepared material. Electrochemical measurements indicated high discharge capacities of ∼230 and 160 mAh/g at C/20 and 1C, respectively, with good cycling performance. In-situ Raman spectroscopic studies revealed extraction of lithium and oxide ions from the lattice followed by rearrangement of cations during the first cycle charging process and extraction of oxide ions followed by insertion of lithium ions back in the structure without any major change during the discharging process. Ex-situ Raman and microscopic measurements on the cathode before and after electrochemical cycling indicated the structural stability of the material. Studies performed on the AlPO 4 -coated composite cathode demonstrate the possibility of using it as nextgeneration cathode material for advanced lithium-ion batteries.

In the present work process methodology was optimized to synthesize oriented barium strontium titanate (BST) (50/50) and (60/40) thin films on strontium titanate (100) and lanthanum aluminate (LAO) (100) substrates by using the chemical solution deposition technique. These films were characterized in terms of their phase formation behavior and structural growth characteristics using x-ray diffraction and atomic force microscopy. A tentative mechanism of the epitaxial growth has been proposed. Films were also characterized in terms of their dielectric properties. The high tunability and low dielectric loss of these films make them attractive for fabricating tunable dielectric devices. Accordingly, we have fabricated eight element coupled microstrip phase shifters and tested them in terms of their degree of phase shift and insertion loss characteristics. An insertion loss of 8.435 dB, phase shift in the order of 320° (2.6–14.5 V/μm) and κ factor (phase shift/dB of loss) of about 38.0°/dB was achieved in BST (60/40) films deposited on LAO (100) substrate which is comparable to the films grown by other film deposition techniques reported in the literature. The microstructure of the sol–gel derived films show surface porosity which may be responsible for the low dielectric strength of these films. Presently, we are studying the sintering mechanism and kinetics of these films in order to improve the density which is believed to further improve the phase shift and lower insertion loss to result in an improved tunability.

We report photovoltaic (PV) effect in multiferroic Bi 0.9 Sm 0.1 Fe 0.95 Co 0.05 O 3 (BSFCO) thin films. Transition metal modified polycrystalline BiFeO 3 (BFO) thin films have been deposited on Pt/TiO 2 /SiO 2 /Si substrate successfully through pulsed laser deposition (PLD). PV response is observed under illumination both in sandwich and lateral electrode configurations. The open-circuit voltage (V oc) and the short-circuit current density (J sc) of the films in sandwich electrode configuration under illumination are measured to be 0.9 V and −0.051 µA cm −2. Additionally, we report piezoresponse for BSFCO films, which confirms ferroelectric piezoelectric behaviour.

We report the switchable photovoltaic effects in graphene/BiFeO3/Pt heterostructures. Pure phase polycrystalline BiFeO3 films were deposited on Pt/TiO2/SiO2/Si substrates by pulse laser deposition. A bilayer graphene was transferred onto the BiFeO3 film which serves as transparent conducting electrodes. The heterostructures showed switchable photovoltaic effect depending on ferroelectric polarization directions indicating depolarization field induced separation of photo-generated carriers. The open circuit voltage (VOC) and short circuit current density (JSC) were measured to be ∼110 mV, ∼92 μA/cm2 in positive polarity and similar values were obtained when the polarity was reversed. The JSC and VOC also showed rapid response (<100 ms) as a function of light exposure time.