We present Raman data on both single-crystal and thin-film samples of the multiferroic PbFe 0.5 Nb 0.5 O 3 . we show first that the number and selection rules of Raman lines is compatible with a face-centered cubic Fm-3m structure, as is known in other ABO 3 relaxors, such as The increase in frequency with increasing temperature for the lowest-energy F 2g phonon mode is particularly unexpected. These changes suggest the transition of crystal structure from an ordered phase to a disordered one near T B . The Raman study revealed phonon anomalies in the vicinity of T m and T N that are attributed to the dynamical behavior of polar nano-regions (PNRs) and spin-phonon coupling due to its relaxor and multiferroic nature respectively, which is well supported by dielectric and magnetic properties of the PFN thin film. Softening of the Fe-O mode was observed near the T N . We correlate the anomalous shift of the Fe-O mode frequency with the normalized square of the magnetization sublattice; agreement with the experimental 2 results suggest strong spin-phonon coupling near T N due to phonon modulation of the superexchange integral, however the shifts in frequency with temperature are small (< 3 cm -1 ).

We study the dielectric properties of nanocomposites in the 0–1.5-GHz frequency regime. These composites consist of electrically insulated metallic nanoparticles and carbon nanotubes, the elongated nanostructures in this study, uniformly dispersed in a dielectric matrix. We find that the properties of these composites depend crucially on the shape and monodispersity of the nanoparticles. While at high concentrations the spherical nanoparticles cause only slight modification of the dielectric function of the composite with respect to the matrix, the elongated nanoparticles produce composites with an enhanced real part of the dielectric function and low imaginary part. Our theory, which is in excellent agreement with these results, suggests specific ways to further improve the dielectric properties of the composites.

Highly oriented Pb(Sc0.5Nb0.25Ta0.25)O3 (PSNT) thin films were prepared by pulsed laser deposition. The transmission electron microscopy studies showed an epitaxial strain between the layers due to the in-plane oriented heterostructure. PSNT showed a decrease in the frequency dependent dielectric maximum temperature (Tm) compared to the bulk and a frequency independent dielectric maximum at 520K around the Burns temperature (Td). The linear fit of the modified Curie-Wiess law at Tm provides γ∼2 and Δ=90K, indicating diffuse phase transition and strong relaxor behavior, further supported by nonlinear fitting of Vogel-Fulcher law. Well-behaved hysteresis loops indicated ferroelectric relaxor nature of the PSNT thin films.

Here we report a low cost electrochemical aqueous solution method for synthesis of high quality two dimensional flat ZnO nano-sheets using standard home use microwave-oven. Independent studies by field emission scanning electron microscopy and high resolution transmission electron microscopy confirm the formation of very thin graphene-like nanosheets of ZnO. The high quality of the sheets is confirmed from a photoluminescence study, which shows the presence of a narrow and sharp band edge emission at 360 nm and the presence of a weak defect related emission peak in the visible region. The conductivity of the nanosheets increases dramatically upon illumination of UV lights as compared to the dark condition. The better crystal quality and excellent photo conductivity ensure these ZnO nanosheets can be used as potential UV detector. It is also found that both response and recovery times of ZnO nano-sheets are very fast and are comparable to those of nanowires and nanorods.

One-dimensional ferroelectric nanostructures, carbon nanotubes (CNT) and CNT-inorganic oxides have recently been studied due to their potential applications for microelectronics. Here, we report coating of a registered array of aligned multi-wall carbon nanotubes (MWCNT) grown on silicon substrates by functional ferroelectric Pb(Zr,Ti)O3 (PZT) which produces structures suitable for commercial prototype memories. Microstructural analysis reveals the crystalline nature of PZT with small nanocrystals aligned in different directions. First-order Raman modes of MWCNT and PZT/MWCNT/n-Si show the high structural quality of CNT before and after PZT deposition at elevated temperature. PZT exists mostly in the monoclinic Cc/Cm phase, which is the origin of the high piezoelectric response in the system. Low-loss square piezoelectric hysteresis obtained for the 3D bottom-up structure confirms the switchability of the device. Current-voltage mapping of the device by conducting atomic force microscopy (c-AFM) indicates very low transient current. Fabrication and functional properties of these hybrid ferroelectric-carbon nanotubes is the first step towards miniaturization for future nanotechnology sensors, actuators, transducers and memory devices.