Abstract. An iterative automatic method is described for the characterization Of lossy piezoelectric materials in the radial resonance mode based on the use of the more general expression for the complex admittance. From the experimental data of Y at four adequately selected frequencies, the constants of the material are determined with the necessaty accuracy to reproduce the piezoelectric behaviour of the sample around resonance. The IEEE-176 Standard procedure has been automatized for the initial estimation of the real parts of the elastic constants. The method is applicable even to those materials in which said standard does not allow one to determine the piezoelectric constants.
An automatic iterative method by which material constants of piezoelectric ceramics may be determined in complex form is described. Measurements are reported on samples with different shapes: thickness expansion and shear plates, and length expansion bars. With the constants provided by this method, the profiles for the conductance, resistance, susceptance and reactance are calculated, for the same sample, in the frequency range containing resonance and anti-resonance, and very good agreement is obtained with respect to the experimental data.
Crystalline and stoichiometric KNbO3 thin films have been grown on (100) oriented MgO substrates by pulsed laser deposition technique. Electron microprobe analysis and Rutherford backscattering spectroscopy of the films show a progressive loss of K with increasing substrate-target distance. To compensate for this K loss the ceramic KNbO3 targets were enriched with K2CO3 powder, pressed at room temperature, and sintered at 650 °C. For a substrate-target distance of 6 cm, targets with [K]/[Nb] molar ratio=2.85 yield stoichiometric KNbO3 films. A partial oxygen pressure of 2×10−2 mbar was optimum for growing transparent films. Films grown between 650 and 700 °C show the KNbO3 crystalline phase with its (110) axis preferentially oriented perpendicular to the surface of the substrate. At these temperatures KNbO3 diffusion into the MgO substrate is observed. Films grown from KNbO3 single crystal targets only contain a Mg4Nb2O9 crystalline layer.
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