Effect of La2O3 modified on pyroelectric properties of 0.69Pb(Mg1/3Nb2/3)O3-0.31PbTiO3 solid solutions

The pyroelectric and polarization properties of La 2 O 3 modified 0.69Pb(Mg 1/3 Nb 2/3 )O 3 -0.31PbTiO 3 solid solution systems were examined by the static technique as a function of temperature. The peak temperature of the pyroelectric coefficient maxima was decreased by La 2 O 3 . From the pyroelectric data, two major anomalies corresponding to the rhombohedral → tetragonal → cubic phase transitions were observed. This suggests that the successive transition of 0.69Pb(Mg 1/3 Nb 2/3 )O 3 -0.31PbTiO 3 systems appeared not to be affected by La 2 O 3 . The optimum conditions for obtaining compositions with improved pyroelectric properties ( p }~ 0.013 C/m 2 K at 126°C, P s }~ 0.197 C/m 2 at 25°C) are a sintering temperature of 1250°C and the nominal addition of 0.03 wt. % La 2 O 3 . The figures of merit ( F v }~ 0.034 m 2 /C, F d }~ 0.357 × 10 −4 Pa 1/2 ) of the composition 0.69Pb(Mg 1/3 Nb 2/3 )O 3 -0.31PbTiO 3 -0.03 wt. % La 2 O 3 are comparable to that of TGS and LiTaO 3 . Also, the piezoelectric constant ( d 33 ) and the electromechanical coupling factor ( k p ) were found to be about 379–422 × 10 −12 C/N and 0.274–0.342 for 0.69PMN-0.31PT- x La systems, respectively.