We present Raman data on both single-crystal and thin-film samples of the multiferroic PbFe${}_{0.5}$Nb${}_{0.5}$O${}_3$ (PFN). We show first that the number and selection rules of Raman lines are compatible with a face-centered-cubic $\mathit{Fm}$-3m structure, as is known in other $\mathit{AB}$O${}_3$ relaxors, such as PbSc${}_{1/2}$Ta${}_{1/2}$O${}_3$. We then compare Raman data with anomalies in magnetization and the dielectric constant near the magnetic-phase-transition temperature ($T_N$), the diffuse ferroelectric-phase-transition temperature ($T_m$), and the pseudostructural-phase transition temperature (Burns temperature ∼$T_B$). The temperature evolution of the Raman spectra for the PFN film shows measurable changes in phonon positions, intensities, and full width at half maxima near 200, 410, and 650 K—temperatures that match well with experimentally observed $T_N$, $T_m$, and $T_B$, respectively. The increase in frequency with increasing temperature for the lowest-energy $F_{2g}$ phonon mode is particularly unexpected. These changes suggest the transition of the crystal structure from an ordered phase to a disordered phase 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 nanoregions and spin-phonon coupling owing 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 results suggests strong spin-phonon coupling near $T_N$ owing to phonon modulation of the superexchange integral; however, the shifts in frequency with temperature are small (<3 cm${}^{-1}$).

The temperature evolution of the dielectric spectra in ${\text{PbFe}}_{0.5}{\text{Nb}}_{0.5}{\text{O}}_3$ (PFN) thin films showed a kink near the Néel temperature $\left(\sim 170\text{K}\right)$ , diffuse phase transition (327–380 K) with frequency dispersion at dielectric maxima temperature, and almost frequency independent maxima at 600 K, suggesting weak magnetoelectric coupling, relaxor behavior, and structural phase transition, respectively. Dielectric properties and magnetic hysteresis revealed the coexistence of relaxor ferroelectricity and weak ferromagnetism at room temperature in PFN films. The magnetization as a function of temperature revealed a cusp in the zero field cooled curve for low magnetic field $\left(\sim 100\text{Oe}\right)$ near 170 K, suggesting spin glasslike behavior.

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.

This study investigates the effect of two different Mn modifiers [MnO2 and Pb(Mn1/3Nb2/3)O3(PMnN)] on the of phase transitions in Pb(Mg1/3Nb2/3)O3-PbZrO3-PbTiO3ceramics. The temperature dependence of polarization derived from measured pyroelectric current indicated change in nature of phase transition with MnO2doping. This phenomenon was supported by the temperature evolution of the linear softening of low lying hard lattice mode as revealed by Raman analysis. The grain size was found to increase with MnO2doping (5X) while decrease with PMnN modification (0.5X). Interestingly, the piezoelectric constant of MnO2 modified composition showed negligible degradation (<1%) even after heat treatment very close to the ferroelectric-paraelectric transition temperature.

Lithium-sulfur (Li-S) batteries have attracted considerable interest as next-generation high-density energy storage devices. However, their practical applications are limited by rapid capacity fading when cycling cells with high mass loading levels. This could be largely attributed to the inferior electron/ion conduction and the severe shuttling effect of soluble polysulfide species. To address these issues, composites of sulfur/ferroelectric nanoparticles/ho ley graphene (S/FNPs/hG) cathodes were fabricated for high-mass-loading S cathodes. The solvent-free and binder-free procedure is enabled using holey graphene as a unique dry-pressable electrode for Li-S batteries. The unique structure of the holey graphene framework ensures fast electron and ion transport within the electrode and affords enough space to mitigate the electrode's volume expansion. Moreover, ferroelectric polarization due to FNPs within S/hG composites induces an internal electric field, which effectively reduces the undesired shuttling effect. With these advantages, the S/FNPs/hG composite cathodes exhibit sustainable and ultrahigh specific capacity up to 1409 mAh/g_s for the S/BTO/hG cathode. A capacity retention value of 90% was obtained for the S/BNTFN/hG battery up to cycle 18. The high mass loading of sulfur ranging from 5.72 to 7.01 mg_s/cm² allows maximum high areal capacity up to ∼10 mAh/cm² for the S/BTO/hG battery and superior rate capability at 0.2 and 0.5 mA/cm². These results suggest sustainable and high-yielding Li-S batteries can be obtained for potential commercial applications.