Electrical conductivity and dielectric behaviour of manganese and vanadium mixed oxide prepared by conventional solid state method

Investigation on electrical conductivity and dielectric properties of manganese (Mn) and vanadium (V) mixed oxides were carried out to study the extrinsic semiconductor behaviour. The XRD pattern shows that Mn–V oxide is multiphase and quantitative phase analysis was performed to determine the relative phases. Overall results indicate that with increasing temperature, the DC conductivity, AC conductivity, dielectric constant, dielectric loss factor and loss tangent of Mn–V mixed oxide increases. Activation energy of AC conduction decreases with increase in frequency, confirms that the hopping conduction is the dominant mechanism. The activation energy of DC conduction ΔEdc is 0.54 eV which is greater than ΔEdc. There are three types of dielectric constant spectrum found in the measuring temperature range 30–250 °C. This is possibly due to the extrinsic behaviour of the Mn–V oxide. Dielectric relaxation characteristic was obtained from the spectrum of the imaginary part of electric modulus. The activation energy of the relaxation process and the relaxation time at infinite temperature are 0.42 eV and 5.40 ps respectively. The Nyquist plot of complex impedance fitted the equivalent circuit model of two RC circuits in series with R and C in parallel. The relaxation time was estimated from the circuit model

Dielectric properties of nickel zinc ferrite-polypropylene composite

Nickel-zinc ferrite (Ni0.2Zn0.8Fe2O4) was prepared using conventional solid-state method. It acts as a filler with polypropylene as the matrix. The samples were characterized by XRD and dielectric measurement was done using Agilent 4291B Impedance/Material Analyzer. It was observed that the composition of 30% doped nickel-zinc ferrite (Ni0.2Zn0.8Fe2O4) gives the highest value of the dielectric constant in the frequency range of 1 MHz to 1.5 GHz at room temperature

Dielectric behavior of Ni0.1Zn0.9Fe2O4-Polypropylene composites at low microwave frequencies.

In the last decade, studies and research toward polymer-clay composites draw significant attention for a suitable filler that can improve mechanical, thermal, electrical, optical and pharmaceutical properties as compared with pure polymer. Ni0.1Zn0.9Fe2O4 (NZF) was prepared using conventional solid-state method. A twophase composite was fabricated with blend filled Ni0.1Zn0.9Fe2O4 added to isotactic polypropylene matrix. The samples were characterized by XRD and dielectric measurements were done using Agilent 4291B Impedance/Material Analyzer. It was observed that the composition of 30 wt% NZF gave the highest dielectric constant in the frequency range of 1 MHz to 1.8 GHz at room temperature

Dielectric and magnetic properties of NiZn-polypropylene and CoZn-polypropylene ferrite composite

Polymer-clay composites exhibit more interesting and improved mechanical, thermal, electrical, optical and pharmaceutical properties as compared to the pure polymer. Guided and motivated by this observation, the main objective of this project is to study the dielectric and magnetic properties of ferrite-polypropylene composites. The effects of different chemical composition of ferrite and different composition of ferrite added to the matrix were investigated. The fillers, MexZn1-xFe2O4 (where Me=Ni, Co; x=0.1, 0.2 and 0.3) were prepared by the conventional solid state method. Different compositions of filler were doped into the polypropylene (PP) and blended to produce ferrite-PP composites. For characterization, X-ray diffraction (XRD) was used to determine the crystalline structure while field emission scanning electron microscopy (FESEM) was used to analyze the microstructure of the ferrites. The dielectric properties were measured using an HP 4284A Precision LCR Meter from 20 Hz to 1 MHz at room temperature. An HP4291B RF Impedance Analyzer was used to measure the dielectric properties and magnetic properties of the samples from 1 MHz to 1.8 GHz at room temperature. From the XRD analysis, it showed that the filler and PP underwent no unwanted reaction during blending process. According to the FESEM images, the average grain diameters of ferrites increased with increasing Zn content in ferrite. The composites with 30 wt% of ferrite added exhibit the highest relative dielectric constant,E' which are 3.44 at 1 kHz and 2.78 at 100 MHz for i0.3Zn0.7Fe2O4-PP composite. The existence of ferrite may take part in compensating the dipole moment of PP. Hence, the E' of 5 wt% - 10 wt% of ferrite composite is lower than pure PP due to the small amount of ferrite (moderate dielectric properties) added which do not give a significant contribution toward PP – based composite. Therefore, a significant improvement on the E' of the composites can be obtained with the addition of ferrite with more than 10 wt%. The addition of ferrite shifted the dielectric loss peak to lower frequencies. A composite with high relative dielectric loss, u" thus it can be utilized as electromagnetic wave absorbing material. By varying the weight ratio of ferrite, the composite can be tailored as an absorbing material at a desired frequency between 10 kHz to 300 kHz. However, the composites do not have significantly improved relative real permeability, u' due to the discontinuity of magnetic flux. 30 wt% of Co0.3Zn0.7Fe2O4 – PP composite has the highest U' which is 1.94 at 50 MHz. As summary, the reinforcement of polymer with filler can enhance the dielectric and magnetic properties of the polymer composites. According to the effective medium theory, the high permittivity or high permeability of the polymer based composites can be obtained by putting the high permittivity or high permeability ceramic particles into the polymer matrices. Therefore, 30 wt% of ferrite-polypropylene composites are given the highest E' and u' among other composites at 20 Hz – 1 MHz and 1 MHz – 1.8 GHz

Electrical properties of mixed oxides of manganese and vanadium prepared by conventional solid state and mechanical alloying methods

Metal oxide of manganese (Mn) and vanadium (V) are widely studied due to their interesting fundamental physical properties. There were several works on Mn-V mixed oxide done previously, but it still lacks comprehensive electrical studies on Mn-V oxide system which can gives more information to describe the mixed oxide. In this project, the investigation toward morphology, electrical conductivity, dielectric properties and thermal diffusivity of the mixed oxides was carried out. The samples were prepared by conventional solid state (SS) and mechanical alloying (MA) methods. The samples were prepared with a ratio of 40 mol% of V2O5 and 60 mol% of 2MnO2 and were sintered at different sintering temperatures from 500 to 800oC and characterized. In the meantime, samples of pure oxides, Mn and V were also prepared to compare with the mixed oxides. X-ray Diffraction confirmed that the samples prepared are multi phases and Rietveld refinement method was employed to estimate the phase composition in each sample. MA method successfully reduced the sintering temperature for the reaction to occur at a much lower temperature compare to SS method. Also, the surfaces of the sample were visualized using Field emission scanning electron microscopy (FESEM) and the average grain size was calculated. From FESEM images, MA method produced very fine particles in nano-scale while SS method in micro-scale. The DC and AC conductivities of the samples showed the semiconducting behavior because the electrical conductivity increases when temperature increased. The Mn-V oxides have lower electrical conductivity as compare to the starting materials. Since the samples are multi phases, hence the dielectric constant obtained is a contribution from different phases. The polarization mechanism in this frequency region (40 to 1 MHz) can be explained by interfacial and dipolar polarization. On the other hand, the spectra of electric modulus and impedance of the samples successfully revealed the dielectric relaxation process which cannot be observed directly from dielectric loss spectrum. Equivalent circuit modeling was adopted to further describe and predict the electrical properties of the material. The samples were successfully fitted to single parallel RC circuit or two parallel RC circuits connected in series. The sample sintered at 500oC prepared using MA method gave the best dielectric properties. This is possibly due to MA method reduces the particle size and increases the grain boundary volume of the sample. Also, the MA series have better thermal stability and gave higher thermal diffusivity compare to SS series where the heat from energy dissipation can be easily transferred for the cooling process. Lastly, a more comprehensive electrical and thermal study on Mn-V oxide system is done and it can be a reference for future researchers

Effect of sintering temperatures on the microstructure and dielectric properties of SrTiO3

Conventional solid state reaction method is a common and effective way to fabricate modern ceramics. For ceramic processing, sintering is an important factor that affects the microstructure evolution, thus optimizing its natural abilities. In this work, Strontium Titanate (ST) ceramic samples sintered at different sintering temperatures were prepared and analyzed by X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM). XRD is used to determine the samples crystallization, while SEM was for microstructure analysis. Dielectric properties of SrTiO3 samples were measured using Agilent 4291B Impedance/material Analyzer in the frequency range of 1 MHz to 1.5 GHz at room temperature. The dielectric constant is constant with respect to frequency and increased after 1 GHz. Dielectric constant of ST increased with increasing sintering temperatures. ST sintered at 1200°C has the highest dielectric constant of 50. The average grain size increases with increasing sintering temperature

Electrical conductivity and dielectric studies of MnO2 doped V2O5

The investigation on electrical conductivity and dielectric properties of mixed oxide of manganese (Mn) and vanadium (V) was carried out to study the mixed oxides response to different frequencies and different measuring temperatures. The frequency and temperature dependence of AC conductivity, dielectric constant and dielectric loss factor of mixed oxides were studied in the frequency range of 40 Hz–1 MHz and a temperature range of 30–250 °C. Since the mixed oxides are multi phase materials, hence the properties of the pure oxides are also presented in this study to discuss the multi phase behaviour of the mixed oxides. The XRD pattern shows the Mn–V oxide is multiphase and quantitative phase analysis was performed to determine the relative phases. The overall results indicate that with increasing temperature, the AC conductivity, dielectric constant, dielectric loss factor and loss tangent of the Mn–V mixed oxide increases. However, it shows an overlap in the dielectric constant at 225 °C and 250 °C due to the V2O5 phase in the mixed oxide. From the AC activation energy, the mixed oxides underwent conduction mechanism transition from band to hopping in the investigated frequency range. The MnV2O6 has relatively good resistivity, therefore the mixed oxide sintered at 550 °C with the highest composition of MnV2O6 gives the highest dielectric constant of 9845 at 1 kHz, and at 250 °C. Keywords: Dielectric properties, Electrical conductivity, Mixed oxides, Manganese oxide, Vanadium oxid

Dielectric properties of Ni0.2Zn0.8Fe2O4-polypropylene composites

Problem statement: In the last decade, the studies and investigation on polymer-based composites have drawn significant attention owing to improvement in their mechanical, thermal, electrical, optical and pharmaceutical properties as compared with pure polymer. Approach: Different compositions of Ni0.2Zn0.8Fe2O4 (NZF) and Polypropylene (PP) can alter the useful properties of polymer-based composites. Hence, the determination toward significant percentage of NZF added into PP can improve the dielectric properties of the composites. NZF was prepared using conventional solid-state method and composites of isotactic PP filled with NZF were fabricated. The dielectric properties of the composite were investigated using Agilent 4284A Precision LCR meter. Results: The results indicated that with increasing ratio of wt% NZF, the dielectric constant and dielectric loss of the composite increases. The composition of 30 wt% NZF gave the highest value of the dielectric constant in the frequency range of 100 Hz-10 kHz at room temperature. Conclusion: The incorporation of ceramic filler improved the dielectric constant and increase the dielectric loss of the composite correspondingly increases its potential use as an absorbing material for electromagnetic waves