(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 (true) pyroelectric coefficient From the dielectric/pyroelectric data of both the unsubstituted (Ba, Sr)TiO3 (BST; with Ba: Sr = 2:1) and the Zr-substituted BST, it was shown that the intrinsic pyroelectric coefficient made a dominant contribution to the net pyroelectric coefficient below the Curie temperature (T-c). On the other hand, the induced pyroelectric coefficient contributes significantly to the net pyroelectric response above T,by virtue of the reduction in the temperature-dependent spontaneous polarization. The behavior of the induced pyroelectric response for the Zr-substituted BST was further analyzed using a semiempirical model based on the concept of a Gaussian distribution of the 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 thermostability of pyroelectric figure-of-merit at near ambient temperature was deduced from the analysis, and it was 10 at. % Zr-substitution with Ba: Sr = 3:1 (ie., Ba0.75Sr0.25Ti0.9Zr0.1O3).