Relaxor-ferroelectrics: An efficient material for waste-heat harvesting

The need for efficient energy utilization is driving research to harvest waste-heat, which is ubiquitous, abundant, and free. Thermal energy harvesting for low power electronic devices using ferroelectric materials is one of the emerging areas of research because they possess spontaneous polarization and exhibit excellent pyroelectric coefficients. These materials are unique as they only sense time-dependent temperature change to generate electric power. We have grown lead-free BaZr_0.2Ti_0.8O₃ (BZT)/Ba_0.7Ca_0.3TiO₃ (BCT) multilayer heterostructures on SrRuO₃ (SRO) buffered SrTiO₃ (STO) single crystal substrates by optimized pulsed laser deposition (PLD) technique. We have developed a device with a capacitive structure of 200 nm thick BZT/BCT multilayer heterostructures sandwiched between platinum top and SRO bottom electrodes. The device demonstrates excellent pyroelectric current of ~600 nA in response to temperature fluctuation of 11 K using a laser diode of wavelength 850 nm with a repetition rate of 0.1 Hz and power 150 mW. Our findings suggest that the relaxor-ferroelectric thin film may be competitive with thermoelectric materials for low-grade thermal harvesting.