The electrostrictor - A new type of electromechanical semiconductor oscillator

Oscillations of tens of kilocycles/sec across a Germanium crystal, subjected to a strong pulsed electric field through a small area metallic contact, have been observed in recent years but left unexplained. A thorough investigation of this phenomenon resulted in establishing the electromechanical nature of the oscillations. Indeed Germanium has been found to exhibit a very large electrostriction, also the electrical oscillations were found to be accompanied with mechanical oscillations of identical frequency; the latter was established to be the natural frequency of the mechanical system (crystal and holder). In a quantitative analysis of the phenomenon the fourth rank tensor of electrostriction for Germanium was measured and found to be unexpectedly large; different possible processes of regeneration were then considered in order to explain the characteristics of the sustained oscillations; as a result the feedback loop Was established to be through the elastoresistive change of resistivity of the Germanium crystal due to the electrostrictively induced strains. Finally an equivalent circuit is obtained for this novel two terminal electromechanical oscillator which is now called the Electrostrictor.