The effects of porosity and grain size on the magnetic properties of NiZn ferrites were examined on groups of specimens with controlled porosity and grain size; both the permeability and the B-H loop were measured. The demagnetizing factor, which is proportional to porosity, was estimated on the basis of the permeability-porosity relation determined. The discussion of the permeability-grain size relation takes into consideration the dependence of domain wall spacing on grain size. The experimental results for the B-H loops indicate that the remanent magnetic flux density is independent of grain size and the coercive field is independent of porosity. Both the remanent magnetic flux density-porosity and the coercive field-grain size relations are explained via the formulas proposed.

Heat generation phenomena and the change of electromechanical properties of piezoelectric ceramics were measured during high-power vibration using samples with similar electromechanical coupling factors but different mechanical quality factors. The change of the electromechanical properties was separately discussed in terms of the temperature dependence and applied voltage dependence. The vibration velocities during high-power vibration were calculated using these two dependences, and were compared with the measured values. In addition to the electromechanical properties, the jump phenomena of the motional admittance circle around the resonant frequency were investigated using constant-voltage and constant-current driving methods.

Lanthanum-modified lead titanate ceramics with a tetragonality of c/a=1.028 to 1.000 were hot-pressed and the dielectric, electromechanical, optical, and mechanical properties were investigated. With decreasing c / a , the Curie point, remanent polarization, coercive field, and electromechanical coupling factors decrease and the transmittance increases. The internal stress was measured using a microindentation technique by changing the indent load. The internal stress increases with increasing c / a in the tetragonal region and the value for the c/a=1.028 sample was 150 MN/m2.

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