Room-temperature crystal structure, local ferroelectric, and magnetic properties of the ${\text{Bi}}_{1-x}{\text{Gd}}_x{\text{FeO}}_3$ $\left(x=0.1,0.2,0.3\right)$ polycrystalline samples have been investigated by x-ray diffraction, piezoresponse force microscopy, and magnetometry techniques. Performed measurements have revealed a sequence of the composition-driven structural phase transitions $R3c\to Pn{2}_{1}a$ (occurs at $x\sim 0.1$ ) and $Pn{2}_{1}a\to Pnma$ (takes place within the concentrational range of $0.2<x<0.3$ ). The latter structural transformation is attributed to the substitution-induced suppression of the polar displacements. Gd substitution has been shown to effectively induce the appearance of the spontaneous magnetization, thus indicating a promising way for improving multiferroic properties of antiferromagnetic ${\text{BiFeO}}_3$ .

In this paper we present the impedance spectroscopy of ternary solid solutions of BiFeO₃, TbFeO₃ and PbTiO₃, prepared by solid-state reaction method. The preliminary structural studies were carried out by x-ray diffraction technique, showing the formation of polycrystalline sample with ABO₃ type of perovskite structure with hexagonal symmetry for Bi_0.8Tb_0.1Pb_0.1Fe_0.9Ti_0.1O₃system at room temperature. Dielectric and impedance study of this ceramic has been characterized in the temperature range 175 - 325 ⁰C and frequency range 100 Hz - 1 MHz. The maximum ferroelectric transition temperature (T_c) of this system was in the range 210 - 225 ⁰C with the dielectric constant having maximum value ~2480 at 1 kHz. The complex impedance graph exhibited one impedance semicircle arc at all reported temperatures, which indicates that the impedance response is a Cole-Cole type relaxation. Single semicircle indicate that the grain effect of the bulk in ceramic. The bulk resistance of the material decreases with increasing temperature showing negative temperature showing a typical semiconducting property, i.e. negative temperature coefficient of resistance (NTCR) behavior.

We report hot filament thermal CVD (HFTCVD) as a new hybrid of hot filament and thermal CVD and demonstrate its feasibility by producing high quality large area strictly monolayer graphene films on Cu substrates. Gradient in gas composition and flow rate that arises due to smart placement of the substrate inside the Ta filament wound alumina tube accompanied by radical formation on Ta due to precracking coupled with substrate mediated physicochemical processes like diffusion, polymerization etc., led to graphene growth. We further confirmed our mechanistic hypothesis by depositing graphene on Ni and SiO₂/Si substrates. HFTCVD can be further extended to dope graphene with various heteroatoms (H, N, and B, etc.,), combine with functional materials (diamond, carbon nanotubes etc.,) and can be extended to all other materials (Si, SiO₂, SiC etc.,) and processes (initiator polymerization, TFT processing) possible by HFCVD and thermal CVD.