High-Frequency Vibrations of Plates Made from Isometric and Tetragonal Crystals

Abstract

The paper deals with thin piezoelectric plates made from the isometric crystals, sodium chlorate and sodium bromate, and the tetragonal crystals, potassium dihydrogen phosphate and ammonium dihydrogen phosphate. Bevelling of crystals is first described, briefly, as a method used for preparing single response crystal units. In the following section the paper discusses the possibilities of getting thickness controlled resonances. The two cuts (zxw) 45° and (zxtw) 45°/54° 44′ (notation according to the 1949 Standards of The Institute of Radio Engineers) give the strongest deformations. The measured frequency constants of numerous round bevelled blanks and their temperature coefficients agree in most cases with the values obtained from calculations based on data from other authors. The resistance, inductance, and quality factor of the equivalent electric circuits are measured. The concordance with calculated values is fairly good if the ratio crystal area/(electrode area) is introduced into the formulas. The NaBrO 3 thickness modes have about the same quality factor as that of quartz, the quality factor of NH 4 H 2 PO 4 is about one order of magnitude smaller.