Piezoelectric measurements of Ni-I boracite by the techniques of admittance circle motional capacitance

Abstract

Abstract Piezoelectric experiments on Ni—I boracite have been made between T = 4.2 K and 320 K. An automatic measuring technique permitting the determination of the entire set of parameters of the electric series equivalent circuit has been developed and is described. It is based on the measurement of the whole admittance circle at piezoelectric resonance. The electromechanical parameters [dcirc]31, ĝ31, and [kcirc]2 31 have been obtained by means of a motional capacitance method and using an independent measurement of êT 31. Measurements have been done under optical control of the ferroelectric and ferromagnetic domain states. Internal loss (1/Q m ) peaks have been observed and were found to increase in temperature (18 K → 20 K and 142 K → 152 K) with frequency (2 MHz → 6 MHz). The only phase transition which can unambiguously be confirmed is the one at 61.5 K.