Electromechanical properties of Pb(Mg1/3Nb2/3)O3–7%PbTiO3 thin films made by pulsed laser deposition

Thin film capacitors of Au/Pb(Mg1/3Nb2/3)O3–7%PbTiO3 [PMN–(0.07)PT]/(La1/2Sr1/2)CoO3 were made by pulsed laser deposition on single crystal {001} MgO substrates. The PMN–(0.07)PT dielectric was perovskite dominated, and demonstrated functional behavior typical of relaxors. Electrostrictive behavior was observed at fields up to 200 kV cm−1, however, the maximum strain was disappointingly low at only ∼0.14%. The macroscopic electromechanical d33 and Q33 coefficients were determined using piezo-response atomic force microscopy. At 100 kV cm−1 the macroscopic Q33 was found to be (2.6±0.2)×10−2 C−2 m4. The crystallographic electrostrictive coefficient was determined using in-situ x-ray diffraction and at the same field found to be significantly higher: (4.9±0.2)×10−2 C−2 m4. Since these electrostrictive coefficients are of the same order of magnitude as found in single crystal experiments (2.5–3.8×10−2 C−2 m4), it appears that the low out-of-plane strain is simply the result of poor polarizability in the thin films. An effective Q13 component of the electrostrictive tensor was also determined, and found to be ∼−0.32 ×10−2 C−2 m4.