Bolometers are a class of devices used for measuring radiant heat by utilising a material having temperature-dependent electrical resistance and an absorbing layer specific to the target frequency band of the incident electromagnetic wave. The absorber layer absorbs the incident radiation and effectively transfers the generated heat to the thermistor layer for electrical readout. There is always a search for materials showing a high-temperature coefficient of radiation (TCR), preferably at room temperature, along with excellent microwave absorption or materials that show the same independently. Magnetic materials show excellent magnetic loss, while carbon-based materials and some semiconducting materials achieve excellent dielectric loss1, an indicator of a good absorber. However, both suffer from poor impedance matching and hence poor microwave absorption. This work consists of the microwave characterisations of V2O5, La0.845Sr0.155MnO3 and a few combinations of polymer composites for use as either the absorber or the thermistor layer. The microwave dielectric properties of these materials will be discussed, along with their microwave absorption properties. A prototypical pixel will be proposed as an imaging device employing the said materials. A general approach for improving impedance mismatch will be discussed. Additionally, the use of metamaterials will be discussed to address the impedance mismatch and enhance the absorption of the incident microwave radiation.
Biography of the Speaker :
PhD Scholar, Department of Physics, IIT Madras
Affiliation of the Speaker :
Guide: Dr. SUBRAMANIAN V