Influence of starting powder milling on magnetic properties of Mn-Zn ferrite

In this paper, the influence of additional sieving and milling of starting industrial Mn-Zn powders on magnetic properties was investigated. The starting powder was milled for 60 minutes, followed by sieving through 325 and 400 meshes. The starting and milled powders were used to fabricate toroid shaped samples sintered at 1200°C for 2 hours. Structural parameters of the fabricated samples were analysed by X-ray diffraction and scanning electron microscopy. Complex permeability, core loss density, and hysteresis were measured using the modified watt-meter method. The complex permeability and hysteresis loop were modelled with a new model proposed in the paper. The core loss density was modelled with the Steinmetz empirical equation. The experimental results and calculations show the significance of the additional milling and sieving process on magnetic properties of Mn-Zn ferrite in the frequency range 0.1-10MHz. These processes increase the relative permeability about 3 times and decrease the core loss 4 times by milling of the starting powder

Tailoring the microstructure of Mn-Zn ferrite to electronic properties

Commercial Mn-Zn ferrite powder was milled in a planetary ball mill for 30-240 minutes. Particle size distribution in the milled powders was analyzed using a laser particle size analyzer and correlated with XRD and SEM analysis of the milled powders. Green disc and torroid samples were sintered in air in the temperature interval 800 -1300oC for 2 hours. SEM/EDS, AFM/MFM analysis of the sintered samples and measurements of their electrical properties such as DC resistance up to 500 MHz enabled establishment of a correlation between the microstructure and properties in the high-frequency range

PERFORMANCE ANALYSIS OF A FLEXIBLE POLYIMIDE BASED DEVICE FOR DISPLACEMENT SENSING

The goal of this paper is to investigate the performance of a wireless passive displacement sensor. Displacement sensor based on the heterogeneous integration process combines traditional fabrication technologies PCB (Printed Circuit Board) and LTCC (Low Temperature Co-fired Technology) with a flexible polyimide foil. The proposed sensor uses the coil as an essential part, multiple spacers and a polyimide foil as a flexible membrane with a piece of ferrite attached to it. With the displacement of the polyimide foil, the ferrite gets closer to the coil causing an increase in its inductance and a decrease of the resonant frequency of the system (coil, ferrite and antenna). Simulation results showed that sensors with equal outer dimensions but different internal structures exhibit different performances. Two prototypes of the sensor with different ferrite dimensions are designed, fabricated and characterized. Finally, their performances are compared

In the frequency range between 1 kHz and 1 MHz

In this paper, a capacitive method for characterization of LTCC tapes in the frequency range between 1kHz and 1MHz using HP 4277A LCZ meter is presented. The principle of operation using a parallel plate capacitor and equivalent circuit as a parallel connection of capacitance and a resistor is explained and characterization of test samples is measured. The fabrication process in LTCC technology and the causes that can produce the changing of characteristic parameters of substrates in fabrication are explained in detail. We indicated the importance of knowing permittivity in the function of frequency during projecting and simulating electronic components and circuits in LTCC technology. Measurements of complex permittivity, loss tangent, Q-factor based on the proposed formulas are made for LTCC tapes samples. Small variation of measured capacitance and loss tangent is obtained, approximately about 2% in whole frequency range. The value of loss tangent is approximately the same as the value specified by manufacturers. The calculated parameters for complex permittivity have bigger values then those recommended by manufacturers before firing. In the process of sintering, sheet density and microstructure of commercial tapes are changed for all used materials, causing changes of electric characteristics, especially permittivity. In the low frequency range, below 50 kHz, there is a higher variation of characteristic parameters. In this range, the parallel resistance of the equivalent circuit is on the top level of the instruments limit and these results are not reliable. A specific user-friendly program is developed which enables automatic control of measurement, recalculation of important values and processing of results

IMPROVED RESISTIVE STRAIN GAGE PRINTED ON FLEXIBLE SUBSTRATE

In this paper, resistive strain gages designed and fabricated in inkjet printing technology with three different silver nanoparticle inks are presented. Inks have different Ag content (15, 20 or 25 wt%) and solvents (water type or organic type). Strain gages were printed on a 50 µm thick polyimide and 140 µm thick PET-based substrate with different printer types (professional and desktop). All printed sensors have the same size (17 mm × 5 mm). To determine the change of resistance due to bending of the steel beam, tensile tests were performed up to 1500 microstrains. Due to performed cycles of loading and unloading of the steel beam, gauge factor and stability of the response of the strain gages are measured. Resistance change was measured with Keithley SourceMeter 2410. For acquisition of measured data, in-house software tool was developed. Measured gauge factors of the sensors are in the range between 1.07 and 2.03 (depending on a used ink, substrate and printer). Results of this research indicate the strain gages with good GF can be produced even with low-cost equipment, such as desktop printer EPSON C88+ and PET-based substrate

Impedance response of pseudobrookite thick films with a sandwich configuration

We have investigated the impedance response of pseudobrookite thick films screen printed on alumina substrate in the temperature interval from room temperature to 350 °C in the frequency range 100 Hz-1 MHz. Two thick film pastes were made containing starting hematite and anatase nanopowders (in the 1:1 and 1:1.33 molar ratio - containing excess anatase), glass fritt and organic vehicle. A sandwich PdAg electrode structure was obtained by first printing a PdAg electrode, followed by 3 layers of PSB paste and a PdAg electrode on top with a mesh structure. Each layer was sintered at 850 °C in a hybrid conveyor furnace. XRD analysis confirmed the formation of pseudobrookite with an orthorhombic crystal structure. SEM analysis of thick film surfaces and cross sections showed the formation of a porous structure with rod-shaped grains. The impedance response of pseudobrookite thick films, showed a decrease with the rise in sample temperature. It was analyzed using an equivalent circuit reflecting the dominant influence of grain boundaries

Influence of starting powder milling on structural properties, complex impedance, electrical conductivity and permeability of Mn–Zn ferrite

In this work we have analyzed how milling starting commercial Mn–Zn powder prior to the sintering process has an influence on electrical conductivity, relative permittivity and complex impedance in the frequency range from 100 Hz to 1 GHz and relative permeability in the frequency range 1–500 MHz. Starting powders additionally were milled for 30, 60, 120 and 240 min followed by sintering disk samples between 900 and 1300 °C. Structural properties were analyzed using XRD and SEM analysis. Milling the starting powder reduced grain and crystallite size, but longer milling leads to agglomeration and consequently an inhomogeneous microstructure that was more expressed at higher sintering temperatures. Milling the starting powder improved relative permeability, reaching a maximum for samples of starting powder milled for 60 min and sintered at 1200 °C

Electrical, mechanical and temperature characterization of commercialy available LTCC dielectric materials

Presented paper deals with mechanical, electrical and thermal properties of several commercially available materials that are widely used for fabrication of electronic components, sensor systems etc. In the LTCC (Low Temperature Co-fired Technology). Having complete and accurate information of material chemical composition, its electrical and mechanical properties are essential for successful design of various components and/or systems. In many cases, available technical documentation provided by the manufacturers contains less information than designers require for complete pre-design analysis of system behavior in real time environment. Three offently exploited commercialy available dielectric materials provided by Heraeus company (Heraeus CT700, Heraeus CT707 and Heraeus CT800) are investigated. Electrical, mechanical and thermal properties analyses have been conducted in order to determine some of the important material properties. A full chemical composition analysis was performed resulting in determination of materials' chemical composition, followed with determination of relative permittivity value, elasticity modulus and relative thermal coefficient value. [Projekat Ministarstva nauke Republike Srbije, br. III 45021

PERFORMANCE ANALYSIS OF A FLEXIBLE POLYIMIDE BASED DEVICE FOR DISPLACEMENT SENSING

Abstract. In this work, two variations of the displacement senso