Intrinsic and coupling-induced elastic nonlinearity of lanthanum-doped lead magnesium niobate-lead titanate electrostrictive ceramic

The elastic nonlinearity of lanthanum-doped lead magnesium niobate-lead titanate electrostrictive ceramic has been investigated by using ultrasonic second-harmonic generation technique and field-induced strain measurement. A large ultrasonic nonlinearity parameter, beta=30, was observed at room temperature, which is more than twice of the values for lead zirconate-lead titanate piezoelectric ceramics. The third-order elastic constant c(111) has been calculated from the beta value. By introducing an effective nonlinearity parameter beta(e) that includes both the intrinsic and the electromechanical coupling generated elastic nonlinearities, the nonlinearity parameter can be accurately characterized. The strong field dependence of the nonlinearity parameter shows excellent potential for designing field tunable nonlinear devices using this material. (C) 2000 American Institute of Physics. [S0003- 6951(00)04335-7].