Wyniki wyszukiwania - BazTech

1

Complex permittivity, permeability and microwave absorbing properties of Co–Ti substituted strontium hexaferrite

Narang S. B., Kaur P., Bahel S.

Materials Science Poland

|

2016

|

Vol. 34, No. 1

19--24

EN

M-type strontium ferrite with compositions SrFe(12-2x)CoxTixO19 (x = 0.0, 0.3, 0.5, 0.7, 1.0), were prepared by two route ceramic method. The effects of Co-Ti substitution on their microstructure, electromagnetic properties, and microwave absorptive behavior were analyzed. The complex permittivity (epsilon'-j epsilon '') and complex permeability (mu'-j mu '') have been measured from 8.2 to 12.4 GHz using a network analyzer. Scanning electron microscope was used to analyze the grain size distribution and porosity of the ferrite. X-ray diffraction confirmed the M-type structure of the doped strontium ferrite. Vibrating sample magnetometer was used to study hysteresis loop of the ferrite. This study suggests that the control of grain size, decrease in coercivity and enhanced values of dielectric constant and loss are effective means to improve microwave absorption. The dielectric constant and loss were enhanced in comparison to the permeability constant and loss over the entire frequency range.

2

Influence of frequency variations on the dielectric properties of Sm doped Ba4La9.33Ti18O54 dielectric ceramics at various temperatures

Bindra Narang S., Bahel S.

Materials Science Poland

|

2010

|

Vol. 28, No. 1

305--312

EN

The dependence of frequency variations on the dielectric properties of Sm substituted barium lanthanum titanate was investigated. Dielectric ceramics based on the Ba4(La1-ySmy)9.33Ti18O54 system, where y = 0.0, 0.3, 0.5, 0.7, were synthesized and subsequently characterized for their structural and dielectric properties. The temperature dependences of the relative permittivity and the dielectric losses were measured in the frequency range from 10 kHz to 10 MHz, for temperatures ranging from 25 °C to 150 °C. The measurement system consisted of an impedance analyzer and a temperature chamber. Substituting Sm for La was an effective way to stabilize the variations in relative permittivity, within the temperature range of interest. No dielectric anomaly was observed in this temperature range. The temperature coefficient of the resonant frequency improved from 273.9 ppm/°C at y = 0.0 to 53.8 ppm/°C at y = 0.7. The relative permittivity of 90.33 and a dielectric loss of 0.09 were obtained at 25 °C for y = 0.5 at 10 MHz; the temperature coefficient of the resonant frequency was 106.8 ppm/°C. The materials under investigation have high relative permittivities, remaining constant under temperature variation, which therefore makes them suitable for applications in communication devices.

3

Dielectric and structural characteristics of Sm doped Ba4La9.33Ti18O54 microwave ceramics

Bahel S., Narang B.

Materials Science Poland

|

2008

|

Vol. 26, No. 3

555--561

EN

The microwave dielectric properties and structural variation of Sm doped Ba4La9.33Ti18O54 have been investigated. Ba4(La(1-y)Smy)9.33Ti18O54, y = 0.0.0.7 ceramics were prepared by conventional solid state route. The electric permittivity and loss tangent were measured using a network analyzer in the frequency range of 0.3.3.0 GHz at room temperature. The loss tangent decreases significantly upon increasing Sm contents, along with a slight reduction in electric permittivity. A relatively good combination of dielectric properties was obtained for y = 0.5 (ε = 83.3 and tanδ = 0.021 at 3.0 GHz). X-ray diffraction and scanning electron microscopy were applied to investigate the microstructure and correlate it with microwave dielectric properties.