Observations on Modes of Vibration and Temperature Coefficients of Quartz Crystal Plates

I T H the increasing demands of the radio industry for a high degree of carrier-frequency stability, considerable attention has been focused recently on the piezo-electric quartz crystal as a circuit element in frequency generating systems. The low damping of these mechanical oscillators, combined with their piezo-electric properties makes them particularly suitable for frequency control where a high degree of constancy is required. The frequency stability of the quartz plates prepared in the usual manner, is however, often not sufficient for m a n y of the demands for constant frequency. For instance such a crystal plate does not compare favorably as a substandard of frequency with a good astronomical clock. To meet the demands for frequency substandards as well as m a n y other practical problems concerning frequency generation in the communication art, it becomes necessary to devise methods for improving the frequency stability of these crystal systems. This involves a study of the m a n y factors upon which this stability depends.