Lead-Free Pyroelectric Materials for Thermal Energy Harvesting: A Comparative Study

Abstract

The thermal energy harvesting potential of different pyroelectric materials including Sr0.5Ba0.5Nb2O5 (SBN), [Bi0.48Na0.4032K0.0768] Sr-0.04(Ti0.975Nb0.025)O-3 (BNT-Nb), Ba0.85Sr0.15Zr0.1Ti0.9O3 (BST-BZT), Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCT-BZT), and Ba0.9Ca0.1TiO3 (BCT) ceramics is compared. Amongst these materials, BCT is found to be best for pyroelectric energy harvesting. Open-circuit voltages were found to be 1.7 V, 500 mV, 650 mV, 600 mV, and 400 mV for BCT, SBN, BCT-BZT, BST-BZT, and BNT-Nb, respectively. BCT is further analyzed, revealing an optimum power output of 0.072 mu W at the optimized cycle frequency (0.06 Hz) and at a load resistance of 18 M Omega. To improve the effectiveness of energy conversion from heat to electricity, the synchronized switch harvesting on inductor (SSHI) technique is experimentally tested on a BCT sample. It is revealed that this concept based on SSHI can significantly increase the amount of power extracted from pyroelectric materials. Compared with 0.072 mu W across a standard circuit in a BCT sample, an enhanced power output of 0.16 mu W and 0.14 mu W is obtained using parallel and series SSHI, respectively at 0.06 Hz. The results reveal that the non-linear processing technique based on SSHI leads to significant power improvement compared to non-switched interface.