Michael Blaszkiewicz

Frequency agile sonic transducer

A solid-state tunable transducer has been developed by incorporating an elastically nonlinear material, silicone rubber, into an electroacoustic transducer made from piezoelectric ceramics. The resonant frequency and mechanical Q of the transducer are tuned mechanically by applying a uniaxial compressive stress to the composite. The resonant frequency is tuned electrically by placing a piezoelectric actuator into the composite and varying the magnitude of the d.c. bias.

Study of the volume fraction, temperature, and pressure dependence of the resistivity in a ceramic-polymer composite using a general effective media theory equation

A quantitative general effective media (GEM) equation is used to describe quantitatively the resistivity of an Fe3O4-epoxy composite system over a large range of volume fractions in terms of the resistivities of each component and two percolation morphology parameters. One parameter is the critical (percolation) volume fraction, φc, and the other is an exponent,t. Preliminary models, also based on the GEM equation, are used to describe the positive temperature coefficient of resistivity (PTC) and the piezoresistivity (uniaxial pressure) of the composite when the composition is near the percolation threshold.

Tunable transducers as smart materials

A solid-state tunable transducer has been developed by incorporating an elastically nonlinear material, silicone rubber, into an electroacoustic transducer made from piezoelectric ceramics. The resonant frequency and mechanical Q of the transducer are tuned mechanically by applying a uniaxial compressive stress to the composite. The resonant frequency is tuned electrically by placing a piezoelectric actuator into the composite and varying the magnitude of the DC bias.<<ETX>>

Investigating Phase Transitions in ABO₃ Perovskites Using Perturbed Angular Correlation Spectroscopy

Abstract Perturbed Angular Correlation (PAC) measurements were performed at several temperatures on BaTiO3, SrTiO3, BaHfO3 ceramic and PbTiO3 powder samples. In the PbTiO3 and BaTiO3 samples, both the tetragonal (ferroelectric) and the cubic (paraelectric) phases were investigated. For the tetragonal phase temperatures, the perturbation functions for PbTiO3 show strongly decreasing electric field gradients (efgs) and increasing linebroadening with increasing temperature. These two features are evidence for an order-disorder phase transition mechanism. Although the data for tetragonal BaTiO3 provide less information, linebroadening is evident, which is not inconsistent with an order-disorder mechanism. Above the Curie temperatures, both compounds show featureless perturbation functions that decay slowly with increasing time. In addition, this interaction shows little temperature sensitivity. Similarly, PAC measurements on cubic BaHfO3 and cubic SrTiO3 show this behavior. The literature reports similar phen...