(BA, SR)TIO3 SYSTEM UNDER DC-BIAS FIELD .2. INDUCED AND INTRINSIC PYROELECTRIC COEFFICIENTS AND FIGURES-OF-MERIT

The pyroelectric coefficient under the applied DC-bias field consists of two terms: (i) induced pyroelectric coefficient, (ii) intrinsic (tr ue) pyroelectric coefficient From the dielectric/pyroelectric data of both the unsubstituted (Ba, Sr)TiO3 (BST; with Ba: Sr = 2:1) and the Z r-substituted BST, it was shown that the intrinsic pyroelectric coeffi cient made a dominant contribution to the net pyroelectric coefficient below the Curie temperature (T-c). On the other hand, the induced pyr oelectric coefficient contributes significantly to the net pyroelectri c response above T,by virtue of the reduction in the temperature-depen dent spontaneous polarization. The behavior of the induced pyroelectri c response for the Zr-substituted BST was further analyzed using a sem iempirical model based on the concept of a Gaussian distribution of th e local Curie points. The two practically important figures-of-merit ( F-V and F-D) under various DC-bias fields were estimated as a function of temperature. An optimum condition of the composition for the therm ostability of pyroelectric figure-of-merit at near ambient temperature was deduced from the analysis, and it was 10 at. % Zr-substitution wi th Ba: Sr = 3:1 (ie., Ba0.75Sr0.25Ti0.9Zr0.1O3).