DOPING EFFECT OF PHOSPHORIC-ACID ON THE FERROELECTRIC CURIE-POINT OF TRIGLYCINE SULFATE

The temperature dependence of the dielectric constant of a phosphoric- acid-doped triglycine sulfate (TGSP) crystal has been measured in the vicinity of the Curie point T-c. The Curie point of TGSP shifts to a l ower temperature with increasing concentration of dopant. It was revea led that the reduced shift of the Curie point Delta T-c/T-c is almost equal to the mole fraction of H3PO4 in the crystal. The number of dipo le moments restrained from reversing due to doping agrees with the num ber of H3PO4 molecules incorporated into the crystal.