Equivalent pyroelectric coefficient of a pyroelectric bimorph structure

A detailed formula for the equivalent pyroelectric coefficient of a bimorph structure acting as a pyroelectric detector was deduced. It is shown that electric fields occur in the structure when it is subjected to a temperature variation, due to the unequal charges generated by the two components. The field dependence of the ferroelectric polarization has to be considered in this case and the (partial derivativeP/partial derivativeE) derivative appears explicitly in the deduced formula. The effect is that the equivalent pyroelectric coefficient has different values for heating and cooling. This could lead to a redressing effect on the pyroelectric signal if the temperature difference varies periodically. The equivalent pyroelectric coefficient is, also, thickness dependent. This fact offers the possibility of designing structures with high values of pyroelectric coefficient compared with the values of the component phases. (C) 2000 American Institute of Physics. [S0021- 8979(00)04701-6].