No abstract

Piezoelectric energy harvesting systems are of interest as a long-term power source for low-power wireless sensors. Transduction from elastic to electrical energy depends on the product of the piezoelectric charge and voltage coefficients; optimization of this figure of merit is an essential step towards improved microelectromechanical energy harvesting devices. This work reports on the composition dependence on the dielectric and piezoelectric properties of epitaxial {001}Pb(Zrx, Ti1−x)O3 films grown by chemical solution deposition and crystallized at 650 °C on (100)Pt//(100)MgO substrates for 0.63 ≤ x ≤ 0.30. The power generation figure of merit shows the greatest magnitude at compositions near x = 0.52, for which e31,f = −12 C/m2 and εr = 420. Lattice parameters were determined as a function of [Zr] to assess when comparisons to single domain properties calculated from Landau-Devonshire theory were appropriate. Furthermore, films doped with 1 at. % Mn had the highest observed figure of merit, four times greater than of AlN.

It was shown by Ouyang et al. [Appl. Phys. Lett. 86, 152901 (2005)] that the piezoelectric e31,f coefficient is largest parallel to the spontaneous polarization in tetragonal PbZrxTi1−xO3 (PZT) films. However, the expected piezoelectric data are typically calculated from phenomenological constants derived from data on ceramic PZT. In this work, the dependence of e31,f on c-axis texture fraction, f001, for {001}PZT thin films was measured by growing films with systematically changed f001 using CaF2, MgO, SrTiO3, and Si substrates. An approximately linear increase in e31,f with f001 was observed for compositions up to 43 mol. % Zr, and 100% c-domain properties were extrapolated. It was demonstrated that c-axis PZT films can achieve e31,f exceeding −12 C/m2 for many tetragonal compositions. The energy harvesting figure of merit, e31,f2/εr, for c-axis PZT films surpassed 0.8 C2/m4. This is larger than the figure of merit of gradient-free PZT films grown on Si substrates by a factor of four.