Morphology-dependent space charge polarization and dielectric relaxation of CdO nanomorphotypes

A versatile approach signifying the morphology-dependent dielectric polarization and relaxation mechanisms of cadmium oxide(CdO)nanosphere,nanoflakes and nanoparallelepiped morphotypes as a function of frequency and temperature is presented.Variation of dielectric property is observed due to the changes of space charge/interfacial polarization resulting from the variations of surface to volume ratio of nanomorphology.Accordingly,colossal dielectric constant value has been observed in CdO nano-sphere having larger surface to volume ratio.The order of dielectric constant(dc)values observed for the present nanomorphologies is:dc of sphere>dc of flakes>dc of parallelepiped resembles the order of surface to volume ratios of the present morphologies respectively.The experimental data of complex impedance values are numerically fitted using theoretical models which provide the information of role of grain resistance on dielectric polarization and Cole–Cole type mechanism of dielectric relaxation process.The activation energies for electron transport are found to be 0.087 eV for spheres,0.074 eV for flakes and 0.067 for parallelepiped nanomorphotypes of CdO.The dielectric and impedance spectroscopic analysis of the present material opens up wide scope for morphology-dependent tuning of nanomaterials for electrical applications.

Magnetic manganese-based composites with multiple loss mechanisms towards broadband absorption

The weak dielectric properties and the lack of magnetic loss of manganese-based absorbers are obstructed as the new generation of electromagnetic wave absorption(EMA)materials applying in microelectronic devices.Herein,the sulfuration and subsequent compounding strategies have been employed to enhance the EMA performance of multi-shell nanosphere-shaped Mn_(2)O_(3)materials.With the narrow bandgap,the as-obtained MnS possesses reinforced electrical conductivity,which is conducive to conductivity loss.More importantly,the presence of potential difference between different phases will form space charge region at the heterogeneous interface,thus favoring interfacial polarization.Additionally,the improvement of magnetic loss is attributed to the presence of Co_(3)O_(4)nanoparticles.Consequently,the composites present enhanced EMA performance than original Mn_(2)O_(3).Specifically,the minimum reflection loss of as-prepared composites is−51.4 dB at the thickness of 1.8 mm and the broad effective absorption bandwidth reaches 6.2 GHz at 1.9 mm.The low matching thickness and high absorption efficiency in this work can provide a convincing reference when designing distinguished manganese-based absorbers.