Estimation of Polarocaloric Contribution to Dielectric Loss in Oriented 0.92Pb(Zn1/3Nb2/3)O3–0.08PbTiO3 Single Crystals

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This study estimates the contribution due to the polarocaloric effect (PCE) to the dielectric losses in $\langle 001\rangle$, $\langle 110\rangle$ and $\langle 111\rangle$ oriented Pb(Zn1/3Nb2/3)O3–8%PbTiO3 (PZN–PT) single crystals. The PCE is computed from the polarization-electric field curves measured under adiabatic conditions. The normalized magnitude of dielectric losses ($\chi''$), given by $\bar{\chi}''=\chi''/f(\varpi)$, where $f(\varpi)$ is function of material parameters, constant electric field heat capacity and thermal conductivity, in the $\langle 100\rangle$, $\langle 110\rangle$ and $\langle 111\rangle$ orientations at ferroelectric to paraelectric phase transitions are of the order 45, 55 and 25 respectively. This large magnitude of $\bar{\chi}''$ indicates that the PCE makes significant contribution to the dielectric absorption at high temperatures in poled state under applied electric field in this material. Further, the plot of PCE as a function of temperature traces the phase transformational characteristics of this system and clearly establishes the existence of intermediate ferroelectric orthorhombic phase in all the orientations.
2003-08-15