Research interest
Thermoelectrics
A Thermoelectric(TE) material can convert heat energy into electricity and vice versa. Since huge amount of heat energy is being released into the environment during various processes (industrial furnaces/chimneys, car exhaust etc.), it is desirable to use TE devices to scavenge the waste heat and turn it into clean energy. However, their low conversion efficiency makes TEs economically nonviable. This efficiency is measured in terms of a dimensionless quantity called the TE figure-of-merit, ZT, where T stands for temperature, and Z is given by: 𝑍 = 𝜎𝑆2⁄𝜅 where 𝜎 and 𝜅 are the electrical and thermal conductivities, and S is the thermopower. TEs with ZT > 2 can enhance the power generation efficiency by 10 % to 15 %. Therefore, it is crucial to discover new TE materials with high ZT. The intermetallic Half-Heusler (HH) alloys (chemical formula: XYZ) are promising materials in this regard. Though traditionally studied for spintronics, recently they have attracted considerable attention for topological and thermoelectric properties.
NASA has been using Radioisotope Thermoelectric Generators (RTGs) for decades. They use radioactive plutonium oxide as a fuel (heat source) and power their deep space probes by converting heat into electricity using thermoelectric material.
Half Heusler structure
(a)Band structure of ZrNiSi (black), dotted line indicate chemical potential corresponding to 5 %, 12.5 % and 15 % electron doping. (b) 12.5 % doped (unfolded), (c-f) Fermi surface of 0 %, 5 %, 12.5 %, 15 % electron doping. The scale bar in (a) is the magnitude (increasing, white-blue-green) of spectral weight, which characterizes the probability of the primitive cell eigenstates contributing to a particular supercell eigenstates of the same energy.
DOS projected onto Ni/Co d-state and Si p–states in NbCoSi. In each panel, the projected DOS has been divided into five regions. The ILDOS iso-surfaces showing the hybridisation of the atomic orbitals in each region for the two compounds are shown in the inset. The iso-values corresponding to these plots vary between 0.0121 to 0.162 e/A ̊ 3.
Multiferroics
Multiferroic materials are those which have combined magnetism, and properties of ferroelectric, ferroelastic and/or other primary ferroics. The coupling between different ferroics make multiferroic materials more unique, interesting and useful for device applications. After the silicon industrial revolution, the demand for multiferroic material was increased significantly due to their possible applications. multiferroic materials have applications in devices such as magnetic data storage, transducer etc. Existence of ferroelectricity and magnetism together is rare because their different requirements, as ferroelectricity needs the presence of d0 orbital and partially filled orbital is required for magnetism.