PIEZOELECTRIC CRYSTALS IN TENSOR FORM 



133 



In an effort to measure these effects, careful measurements have been made 

 of the temperature expansions of the three axes X, Y and Z. The results 

 are shown by Table II. On account of the small change in dimension from 



(lO-* 



O -16 



at -18 



-40 -35 -30 -25 -20 -15 -10 -5 5 10 15 20 25 30 35 



TEMPERATURE IN DEGREES CENTIGRADE 



Fig. 7. — Temperature expansion curve along an axis 45° between Y and Z as a 

 function of temperature. 



the Standard curve it is difiScult to pick out the spontaneous components 

 by plotting a cur\-e. By expressing the expansion in the form of the 

 equation 



AL 



^ = ai(r-25) + 02(^-25)' + ^3(^-25)' 



(170) 



