Applications for Pyroelectric Ceramics

Pyroelectric ceramics can be used to detect any radiation that produces a change in the temperature of the crystal, but are generally used for IR detection. Because of their extreme sensitivity a rise in temperature of less than one-thousandth of a degree can be detected. This property finds application in devices such as intruder alarms, thermal imaging, and geographic mapping. 

The uses of dielectrics range from capacitors for storing charge to ultrasound imaging for medical applications. We separate dielectrics from insulators, which we described in Chapter 30, because dielectrics have permanent electric dipoles. If the resultant polarization is spontaneous we have ferroelectrics. This topic is essentially exclusive ceramic materials. Although some polymers are ferroelectric they do not find as wide use as ceramics. And metals cannot be ferroelectric because the charge is not localized. 

The requirement of a permanent dipole moment limits useful dielectrics to a select few crystal structures. So the topic of crystallography is once again important, but we cannot predict ferroelectricity by considering only crystal structure. The most important of the ferroelectric crystals are perovskites. By now you should be gaining an appreciation of the significance of this crystal structure and we still have some important magnetic perovskites to describe in Chapter 33. 

Hankel, Wilhelm Gottlieb (1814-1899) (father of Herman Hankel) proposed the word piezoelectricity in 1881. He taught for 10 years in Halle and then moved to Leipzig in 1849 where he was Professor for 40 years. His thesis was titled De thermoelectricitate crystallorum . Pierre and Jacques Curie had discovered 

Seignette, Pierre (1660-1719) was a French pharmacist who first prepared Rochelle salt in c. 1675. In the early literature the phenomenon of ferroelectricity was more often referred to as Seignette-electricity  

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