The pyroelectric property of $Pb_{1-x}La_xTiO_3$ ceramics in a range of $1.3 - 4.5 ㎛ fabricated by conventional solid sintering, was investigated as a function of poling field.
The pyroelectric coefficient of the 4.1 ㎛ of $Pb_{0.9}La_{0.1}TiO_3$ ceramics was higher than those of the 1.3 ㎛ and 1.7 ㎛ of $Pb_{0.9}La_{0.1}TiO_3$ ceramics at a low poling field and the pyroelectric coefficient was $25nC/㎠K$ at 4kV/mm poling field regardless of grain size.
The pyroelectric coefficient of the 4.5 ㎛ of $Pb_{0.8}La_{0.2}TiO_3$ ceramics was higher than that of the 2.2 ㎛ of $Pb_{0.8}La_{0.2}TiO_3$ ceramics at 0.5 kV/mm poling field. The saturation of pyroelectric coefficient in $Pb_{0.8}La_{0.2}TiO_3$ ceramics occurred more easily than that in $Pb_{0.9}La_{0.1}TiO_3$ ceramics.
In order to explain this phenomenon, the intrinsic and extrinsic effects in view of the definition of the pyroelectric coefficient were introduced. The intrinsic effect on the pyroelectric coefficient was considered as the spontaneous polarization with temperature, related to the tetragonal ratio with temperature. The extrinsic effects on the pyroelectric coefficient were considered as 90° domain wall motion with temperature, related to the change of $I_{002}$ with temperature(relative integrated intensity of (002) peak), and 180° domain wall motion with temperature. Also the quantity of 90° and 180° domain switching during poling treatment were considered in order to explain the pyroelectric coefficient of $Pb_{1-x}La_xTiO_3$ ceramics.
The change of spontaneous polarization and 90° domain wall motion with temperature had no effects on the pyroelectric coefficient of $Pb_{1-x}La_xTiO_3$ ceramics. Also, 90° domain switching during poling treatment had no effect on the pyroelectric coefficient of $Pb_{1-x}La_xTiO_3$ ceramics. In this study, it could be seen that the pyroelectric coefficient of $Pb_{1-x}La_xTiO_3$ ceramics was related to the quantity of 180° domain switching during poling treatment.
The pyroelectric coefficients of $Pb_{1-x}La_xTiO_3$ ceramics increased with domain size at a low poling field. This result means that the quantity of 180° domain switching during poling treatment increased with domain size.
Figure-of-merits in $Pb_{1-x}La_xTiO_3$ ceramics were studied for application. As tetragonal ratio of $Pb_{1-x}La_xTiO_3$ ceramics decreased, the figure-of-merit of $Pb_{1-x}La_xTiO_3$ ceramics increased in a low poling field.
