Ceramics made of barium titanate, lead zirconate, and lead titanate exhibit this material property, making such materials useful for ultrasonic transducers. For similar reasons, rochelle salt was used in early crystal microphones. For 10 points—name 
Ceramics made of barium titanate, lead zirconate, and lead titanate exhibit this material property, making such materials useful for ultrasonic transducers. For similar reasons, rochelle salt was used in early crystal microphones. For 10 points—name this effect, which explains the use of quartz in watches, in which a mechanical force upon a crystal produces a charge.
Ceramics made of barium titanate, lead zirconate, and lead titanate exhibit this material property, making such materials useful for ultrasonic transducers.
{piezoelectric} effect [or {piezoelectricity}]