Dielectric and piezoelectric properties of sol–gel derived lead magnesium niobium titanate films with different textures

The piezoelectric and dielectric constants for Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT, 70/30) films with different orientations were measured. PMN–PT films were deposited on Pt(111)-passivated silicon substrates using a modified sol–gel process. The room temperature dielectric constants K for the {100}-oriented films were 2500–2600, while K for {111}-oriented films were 1900–2000. In both cases tan δ was less than 0.03. The dependence of the piezoelectric coefficient d31 of the PMN–PT films on the poling fields was investigated. The d31 coefficients of {100}-oriented PMN–PT films were found to range from −28 to −69 pC/N with poling field. The {100}-oriented PMN–PT films showed larger piezoelectric coefficient than {111}-oriented films. The d33 coefficients of the 1.5 μm thick {100} oriented PMN–PT films were ∼170–183 pC/N. The aging rate of −d31 was ∼4%–10%/decade.