Effect of poling direction and porosity on piezoelectric figures of merit: A numerical study Raj Kiran, Anuruddh Kumar, Rajeev Kumar and Rahul Vaish Eur. Phys. J. Plus, 134 3 (2019) 103 Published online: 15 March 2019 DOI: 10.1140/epjp/i2019-12458-8