Triglycine phosphate

Piezoelectric quartz, Rochelle salt, ammonium and potassium dihydrogen phosphates, ethylenediamine tartrate, triglycine phosphate... 

For room temperature operation, a most attractive thermal detector is the pyroelectric element. It is a small capacitor with a dielectric material that possesses a temperature sensitive dipole moment. So far, the most successful dielectric is triglycine phosphate (TGS), particularly if doped with L-alanine. Its Curie point is at 49 °C and, consequently, it must be operated below that temperature. (Above the Curie point, these dielectrics lose their pyroelectric properties.) Other suitable materials include lithium tantalate and strontium barium niobate. The voltage across a capacitor of charge Q is... 

For ferroelectrics that undergo a second-order transition (e.g., triglycine sulfate, Rochelle salt, and dihydrogen phosphate) 0c- The change in R is continuous for a second-order transitioa... 

---