Stress insensitive NiCuZn ferrite compositions for microinductor applications

N. Ramamanohar Reddy,Sri Krishnadevaraya University,G. Rajitha,K.V. Sivakumar,V.R.K. Murthy 한국물리학회 2009 Current Applied Physics Vol.9 No.3

Two series of stoichiometric and iron deficient NiCuZn ferrites were prepared by the conventional ceramic method. The formation of single phase was confirmed by X-ray diffraction in pure ferrites and a second phase was noticed in SiO2 added ferrite samples. Initial permeability measurements on these samples were carried out in the temperature range of 30–300 ℃. The effect of external applied stress on the open magnetic circuit type coil with these ferrite cores was studied by applying uniaxial compressive stress parallel to the magnetizing direction and the change in the inductance was measured. These studies show that stress sensitivity is more in stoichiometric ferrite samples than in iron deficient ferrite samples. In order to make them stress insensitive various amounts of SiO2 were added and the stress insensitivity was examined. SiO2 addition was found to be effective in reducing the stress sensitivity. This was confirmed by elastic behaviour studies at room temperature on these ferrite samples by employing composite oscillator technique. These ferrite compositions have been developed for their use as core materials for microinductor applications. Two series of stoichiometric and iron deficient NiCuZn ferrites were prepared by the conventional ceramic method. The formation of single phase was confirmed by X-ray diffraction in pure ferrites and a second phase was noticed in SiO2 added ferrite samples. Initial permeability measurements on these samples were carried out in the temperature range of 30–300 ℃. The effect of external applied stress on the open magnetic circuit type coil with these ferrite cores was studied by applying uniaxial compressive stress parallel to the magnetizing direction and the change in the inductance was measured. These studies show that stress sensitivity is more in stoichiometric ferrite samples than in iron deficient ferrite samples. In order to make them stress insensitive various amounts of SiO2 were added and the stress insensitivity was examined. SiO2 addition was found to be effective in reducing the stress sensitivity. This was confirmed by elastic behaviour studies at room temperature on these ferrite samples by employing composite oscillator technique. These ferrite compositions have been developed for their use as core materials for microinductor applications.

Microwave sintering of iron deficient Ni–Cu–Zn ferrites for multilayer chip inductors

M. Penchal Reddy,W. Madhuri,G. Balakrishnaiah,N. Ramamanohar Reddy,K.V. Sivakumar,V.R.K. Murthy,R. Ramakrishna Reddy 한국물리학회 2011 Current Applied Physics Vol.11 No.2

This study was aimed at the low temperature synthesis of iron deficient samples of Ni―Cu―Zn ferrite using the microwave sintering technique. The samples were sintered at 950 ℃ for 30 min. Microstuctural and structural analyses were carried out using a scanning electron microscope (SEM) and X-ray diffraction (XRD), respectively. The lattice parameter was found to increase with increasing nickel concentration. The porosity calculated using X-ray density and measured density also shows a decreasing behavior with increasing nickel concentration. The variation of saturation magnetization was studied as a function of nickel concentration. All the compositions indicate that they are ferrimagnetic in nature. Initial permeability plotted against temperature at 10 kHz showed a sharp drop at Curie transition temperature and values observed at transition are found to be dependent on the nickel concentration. The dielectric constant, dielectric loss tangent and ac conductivity of all samples were measured at room temperature as a function of frequency. These parameters decrease with increase in frequency for all of the samples. The present ferrites are well suitable for the application in multilayer chip inductor due to its low temperature sinterability, good magnetic properties and low loss at high frequency.

Synthesis and Physical Characterization of -Fe2O3 and (+ )-Fe2O3 Nanoparticles

P. Bhavani,N. Ramamanohar Reddy,I. Venkata Subba Reddy 한국물리학회 2017 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.70 No.2

Magnetic nanoparticles were synthesized at different hydrothermal temperatures (HT; 100, 130, 160 and 190 C) by using a facile hydrothermal route combined with a subsequent calcination process. The calcined materials were analyzed for phase, microstructure, and magnetic and dielectric properties through different characterization techniques. The structural analyses revealed that the material prepared at a HT of 100 C and sequentially calcined at 300 C for 3 h showed a high degree of the maghemite structure. On the other hand calcined materials showed a small additional peak belonging to the hematite structure. FESEM micrographs of the materials calcined at HT, of 100 C and 190 C showed spherical-like nanoparticles with diameters in range 30 - 54 nm. Materials prepared at a HT of 160 C followed by calcination at 300 C for 3 h exhibited the highest saturation magnetization, Ms = 67 emu/g, with a lower coercivity; all materials were in a single domain state. A high dielectric constant (105.54) was observed for the calcined material that had been prepared at a HT of 130 C. The dielectric properties of synthesized materials showed an almost frequency- independent behavior.

Enhanced mangnetoelectric voltage in multiferroic particulate Ni0.83Co0.15Cu0.02Fe1.9O4- δ/PbZr0.52Ti0.48O3 composites – dielectric, piezoelectric and magnetic properties

M. Venkata Ramanaa,N. Ramamanohar Reddy,G. Sreenivasulu,K.V. Siva kumar,B.S. Murty,V.R.K. Murthy 한국물리학회 2009 Current Applied Physics Vol.9 No.5

Multiferroic particulate composites of Ni0.83Co0.15Cu0.02Fe1.9O4-δ – NCCF and lead zirconate titanate (PZT) were prepared conventional ceramic method. The generic formulae x NCCF + (1-x) PZT where x = 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6 mole fractions. The presence of two phases in multiferroic was confirmed with XRD technique. The dielectric constant and loss tangent were studied as a function of frequency (100 Hz to 1 M Hz) and temperature (30–500 ℃). The piezoelectric coefficient d33 were also studied on these particulate composites. The hysteresis behaviour was studied to understand the magnetic properties such as saturation magnetization (Ms) and magnetic moment (μB). The static magnetoelectric (ME) voltage coefficient was measured as a function of dc magnetic bias field. A high value of ME output (3151 mV/Oe.cm) was obtained in the composite containing 50% highly magnetostrictive ferrite component NCCF – 50% highly piezoelectric ferroelectric component PZT. These multiferroic particulate composites are used as phase shifters, magnetic sensors, cables etc. Multiferroic particulate composites of Ni0.83Co0.15Cu0.02Fe1.9O4-δ – NCCF and lead zirconate titanate (PZT) were prepared conventional ceramic method. The generic formulae x NCCF + (1-x) PZT where x = 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6 mole fractions. The presence of two phases in multiferroic was confirmed with XRD technique. The dielectric constant and loss tangent were studied as a function of frequency (100 Hz to 1 M Hz) and temperature (30–500 ℃). The piezoelectric coefficient d33 were also studied on these particulate composites. The hysteresis behaviour was studied to understand the magnetic properties such as saturation magnetization (Ms) and magnetic moment (μB). The static magnetoelectric (ME) voltage coefficient was measured as a function of dc magnetic bias field. A high value of ME output (3151 mV/Oe.cm) was obtained in the composite containing 50% highly magnetostrictive ferrite component NCCF – 50% highly piezoelectric ferroelectric component PZT. These multiferroic particulate composites are used as phase shifters, magnetic sensors, cables etc.