DIELECTRIC AND PYROELECTRIC PROPERTIES OF LANTHANUM-MODIFIED PB(MG1 3NB2/3)O-3-PB(MG1/3TA2/3)O-3-PBTIO3 CERAMICS/

The dielectric and the pyroelectric properties of the 0.4(Pb1-3x/2Lax) (Mg1/3Nb2/3)O-3 - 0.3Pb(Mg1/3Ta2/3)O-3 - 0.3PbTiO(3) (0.4 PMN - 0.3 PM T - 0.3 PT - xLa) solid solution ceramics were investigated. The diele ctric constant and loss of the ceramic samples were determined. The py roelectric coefficient and the spontaneous polarization were measured by the static Byer-Roundy method as a function of temperature and for various compositions in the La-doped PMN - PMT - PT system. Lanthanum doping in this system resulted in a reduction of the grain size, a shi fting of the T-C, by similar to 15 degrees C/mole%, downward, a slight ly reduced dielectric constant and pyroelectric coefficient, and more dielectric ordering. Compositions near 0.4PMN - 0.3PMT - 0.3PT - 0.005 La were identified as having maximum spontaneous polarization and high pyroelectric figures of merit near room temperature. The pyroelectric figure of merit (F-V, F-D) of these ceramics is comparable to the val ues published for TGS or LiTaO3.