Temperature sensitivity of plate modes in ST quartz

On considering 13 modes with shear horizontal (SH) polarization, propagating perpendicular to the x-axis in a ST quartz plate, it is experimentally shown and theoretically verified how the temperature coefficient of delay (TCD) and its behavior vs. temperature depend monotonically on the order n of the mode. This property is attributed to the different sensitivities of the modes towards temperature variations in c/sub 12/, c/sub 14/ and c/sub 44/ elastic moduli. The modes sensitivities towards density /spl rho/, elastic moduli c/sub 11/, c/sub 13/, c/sub 33/ and plate thickness h are either temperature independent or negligibly small. The best thermal stability (TCD/spl ap/0) over the widest temperature range (2-92/spl deg/C) has been detected for the 6/sup th/ mode, while the largest one (350 ppm//spl deg/C) has been measured for the 13/sup th/ mode, at 47/spl deg/C. For comparison, five Lamb modes, propagating along the x-direction in the same quartz plate, show a non monotonic dependence of the thermal coefficient on the mode number, a temperature independent TCD in the range 2-92/spl deg/C, a minimum and maximum value of the TCD (/spl ap/0.7 ppm//spl deg/C and /spl ap/100 ppm//spl deg/C) for the 0/sup th/ symmetric mode and for the 1/sup st/ anti-symmetric mode, respectively.