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Cobalt ferrites have attracted extraordinary attention due to their high coercivity, chemical stability, and mechanical hardness. Lanthanum doped-cobalt ferrites having chemical formula CoLaxFe2-xO4 with composition x = (0.00, 0.015, 0.045, 0.060) were synthesized by chemical co-precipitation method. The prepared samples were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, and current-voltage (I-V) technique. The structure of the crystal was analyzed by X-ray diffraction. The crystallite size of nanoparticles was examined in the range of 21–25 nm, and a fluctuating trend was found with the inclusion of La3+ cations. The X-ray diffraction patterns verify the contraction of lattice constant and unit cell volume with the substitution of La3+ cations except for the concentration of x = 0.060. Lattice constant was in the range of 8.34 A–8.41 A while unit volume cell was in the range of 580 A3–596 A3. The resistivity of all samples was calculated by the application of two probes I-V technique. The maximum resistivity of the order of 81.129 × 105 Ω cm was found for the concentration of x = 0.060 at 723 K which makes it useful for high-frequency gimmicks applications. The resistivity and drift mobility were found inversely related to each other. The inverse relation low-frequency absorption band and high-frequency absorption bands were analyzed by Fourier-transform infrared spectroscopy technique.

Optimization of suitable electrode material flashing high electrochemical performance is the main hindrance in energy storage applications. Metal oxide-based electrode materials are promising candidate which greatly promotes the sustainable development. Herein, strontium oxide (SrO) is synthesized from sonochemical method followed by calcination. Incorporating polyaniline (PANI) and graphene (Gr) intensify the materials performance. Three asymmetric devices are designed using SrO, its composites (SrO/PANI and SrO/PANI/Gr) and activated carbon (AC) as an electrode and electrolyte-soaked separators are sandwiched in solidly packed cell assembly. Electrochemical measurements are performed to scrutinize the inherent properties. After that, Dunn’s model is applied to evaluate the capacitive and diffusion-controlled contributions. The obtained result divulges that SrO/PANI/Gr//AC exhibits more diffusive-controlled contribution and reveals a battery type behavior due to the contribution of PANI in redox reactions. Thus, this work delivers a route to synthesize metal oxides-based composites and a systematic approach to analyze the charge storage mechanism in asymmetric supercapacitors.

Charge carrier modulation of graphene-based field effect transistors (GFETs) is the key factor to utilize and enhance its fascinating properties for technological applicability. Here, we have demonstrated the gate-dependent tweaking of electrical properties of graphene devices by application of honey as a top gate dielectric. Electrical characterization of dual-gated GFET is elucidated at different top and back-gate voltages. A charge neutrality point is fine-tuned by varying the top gate voltage (Vtg) from + 3 to − 4 V. The change in carrier density is clearly observed from 3.66 × 1012 to 2.15 × 1011 cm−2 at + 3 to − 4 Vtg. The charge carrier mobility of gel-gated GFET is increased significantly to 5376 cm2/V ⋅ sec by increasing top-gate voltages up to − 4 V. Result demonstrates a cost-effective, facile and rapid fabrication of top-gated devices and suggest natural dielectric materials as good candidate to replace conventionally available gate dielectrics in FET technology.