Behavior of stress-induced charges in cement containing quartz crystals

The recombination process of electric charges induced by stress release has been measured fur cement samples embedded within quartz crystals to invest igate the behavior of piezo-compensating charges in quartz-bearing rocks. T he stress with a release constant tau of sigma (t) = Delta sigmae(-t/tau) l ed to a theoretical pulse charge density q(t) = alpha Delta sigma{epsilonp/ (tau - epsilon rho)} (e(-t/tau) - e(-t/epsilon rho)), where alpha, epsilon and rho are the piezoelectric coefficient. permittivity and resistivity, re spectively. The induced charges appeared on a sample measured with non-cont acting electrodes depending on the number and orientation of synthetic quar tz crystals, and two decay time constants of 0.25 and 2.5 s were obtained. The apparent piezoelectric coefficient for a sample with one piece of quart z was 1.0 x 10(-15) C/N. However, the coefficients fur samples with two pie ces of quartz, which were arranged in the same or alternate directions, wer e 4.1 x 10(-15) and 1.7 x 10(-15) C/N, respectively. The behavior of piezo- compensating charges around quartz crystals in conductive cement suggests f erroelectric charge migration through the measurements of depolarization cu rrent.