268 THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1954 



Ultrasonic waves (shear on longitudinal) in the 10-30 mc range are trans- 

 mitted down a fused sihca rod, through a polystj-rene or silicone one-quarter 

 wavelength seal, and into the solid specimen. Measurement of reflections 

 within the specimen yields values for velocities of propagation and elastic 

 constants. Data obtained over a temperature range of 78° to 300°K for 

 silicon and germanium single crystals, and 1.6° to 300°K for fused silica are 

 listed. For the latter, a high loss is noted, with an indicated maximum near 

 30°K. 



Merz, W. J.i 



Double Hysteresis Loop of BaTiO:; at the Curie Point, Phys. Rev., 

 91, pp. 513-517, Aug. 1, 1953 (Monograph 2166). 



It is known that the Curie point of the ferroelectric BaTiOs shifts to higher 

 temperatures when a dc bias field is applied. If the crystal shows a sharp 

 transition, we expect by applying an ac field at the Curie temperature that 

 the crystal would become alternately ferroelectric and nonferroelectric in 

 the cycle of the ac field. This can be seen in the shape of the hysteresis loop 

 at temperatures slightly above e. In the center of the polarization P versus 

 field E plot, we observe a linear behavior corresponding to the paraelectric 

 state of BaTiOs above 9. At both high voltage ends, however, we observe a 

 hysteresis loop corresponding to the ferroelectric state. A change in tempera- 

 ture causes a change in size and shape of the double hysteresis loops, ranging 

 from a line with curves at the ends (higher temperature) to two ovei lapping 

 loops (lower temperature). The results obtained allow us to calculate the 

 different constants in the free-energy expression of Devonshire and Slater. 

 One of the results shows that the transition is of the first order since the P* 

 term turns out to be negative. The properties of the hysteresis loops are 

 discussed, especially the large spontaneous electrical polarization and the 

 low coercive field strength. 



Moore, E. F., see C. E. Shannon. 



Morrison, J.^ 



Leak Control Tube., Rev. Sei. Instr, 24, pp. 564-547, July, 1953. 



Phelps, W. A., see T. A. Jones. 



Prince, M. B.^ 



Experimental Confirmation of Relation Between Pulse Drift Mobility 

 and Charge Carrier Drift Mobility in Germanium, Phys. Rev., 91, 

 pp. 271-272, July 15, 1953 (Monograph 2168). 



Experimental data of drift moliilities of minority carriers in germanium are 



1 Bell Telephone Laboratories. 



