PZT-based high coupling with low permittivity thin films

PZT-based piezoelectric thin films will make better piezoelectric devices including piezoelectric energy harvesting (EH) power MEMS, when the piezoelectric thin films show high electromechanical coupling and/or high piezoelectric constants with low permittivity. The piezoelectric thin films are mostly polycrystalline structure with high piezoelectric constants and high dielectric constants, i.e. ε*=300-1300 and e_31,f = -8 ~ - 12C/m². Recently we have found thin films of single c-domain/single crystal PZT-based ternary perovskite, Pb(Mn,Nb)-PZT, exhibit exotic properties, i.e. high coupling and/or high piezoelectric constants with low dielectric constants opposed to the PZT-based thin films. The relative dielectric constants are as low as 100 with e_31,f = -12 C/m². The low dielectric constants achieve high values of Figures of Merit for the EH-MEMS. This paper will discuss on the origin of the exotic dielectric and piezoelectric properties of the single c-domain/single crystal thin films in comparison with bulk PZT-based ceramics.