Abstract :
Two crystals of the monoclinic sphenoidal class have been found which have modes of vibration with zero temperature coefficients of frequency, high electromechanical coupling constants, and high Q´s or low dissipation. These properties make it appear probable that such crystals may have a considerable use in filters and oscillators as a substitute for quartz, which is difficult to obtain in large sizes. These crystals are ethylene diamine tartrate (EDT) having the chemical formula C6H14N2O6, and di-potassium tartrate (DKT) having the formula K2C4H4O6-1/2 H2O. The paper describes the properties of EDT, since this crystal has been found more advantageous than DKT. The 13 elastic constants, the 8 piezoelectric constants, and the 4 dielectric constants have been measured over a temperature range, and from these measurements the regions of low temperature coefficients and high electromechanical coupling have been located. Six low-temperature-coefficient cuts have been discovered and the properties of these cuts are given. These cuts are being applied in the crystal channel filters of the long-distance telephone system, and may be applied to the control of oscillators.
