3-Deazaneplanocin A Magnetic materials C Impedance spectroscopy C
NiFe2O4 (NFO) powders were prepared by the sol–gel auto-combustion method. Analytical grade ferric nitrate (Fe(NO3)3·9H2O) (purity >99%), and nickel nitrate (Ni(NO3)2·6H2O) (purity >99%), obtained from Thomas Baker Company, were used as the starting materials. Stoichiometric amount of metal nitrates and fuel (DL-alanine (NH2CH2CH2COOH)), obtained from Thomas Baker, were dissolved in distilled water. Ferric nitrate and nickel nitrate were dissolved in distilled water with molar ratio of Ni to Fe (1:2), and 5 mol/L of nitric acid, and 2 M DL-alanine were added to the aqueous solution of nickel and ferric nitrates. The reactants are combined in a molar proportion of 1:2:2 of Ni (NO3)2·6H2O:Fe (NO3)3·9H2O:CH3CH(NH2)·COOH, respectively. The fuel-nitrate solution was stirred continuously for 2 h with constant heating at 80 °C to initiate a self-propagating 3-Deazaneplanocin A reaction. The obtained as-burnt powder was mixed thoroughly to a fine powder by grinding, and annealed at 800 °C for 2 h. After annealing, the powder was mixed with a binder [2 wt% polyvinyl alcohol (PVA)] and pressed into pellets of 1 mm thickness and 10 mm diameter using a hydraulic press (500 MPa). The pellets were sintered at three different temperatures 1100 °C, 1200 °C and 1300 °C for 3 h, and their density was determined using the Archimedes method. The phase formation was examined by X-ray diffraction (XRD) spectra collected with Cu-Kα radiation using a Bruker D-8 Advance X-ray diffractometer. The microstructure and grain growth were examined on fractured ceramic surfaces using scanning electron microscopy (JSM 6610 LV, JEOL). Raman spectra were recorded at room temperature using Invia model Renishaw Raman spectrometer using an excitation source having wavelength of 785 nm. The spot size of the laser was 1 μm2 using a 100× objective and the laser power was kept at 1.0 mW, and provide a resolution of 0.5 cm−1. For electrical measurements the sintered ceramic discs were electroded using a fired-on silver paste, and fired at 500 °C for 30 min. The leakage current was measured using a 614 Keithley electrometer under a constant dc voltage of 12 V to determine the dc conductivity. The dielectric response in the frequency range (10−2–106 Hz) was analyzed using a Novacontrol broadband dielectric analyzer, and the magnetic properties on ceramic pieces were measured using a vibrating sample magnetometer (Model micro sense EV9).