Temperature dependence of the dielectric tunability near the critical endpoint in Pb(Zn_1/3Nb_2/3)O₃ –PbTiO₃

ABSTRACT

Dielectric permittivities under the dc field applied along the [001]_c direction (in the cubic coordinate) have been measured in Pb(Zn_1/3Nb_2/3)O₃-7% PbTiO₃ (PZN-7%PT), and the ferroelectric critical endpoint (CEP) has been found at 171 °C and 1.3 kV/cm on the temperature-field phase diagram. Near the critical tempeature, the dielectric tunability has been studied with the emphasis put on its temperature dependence. A large dielectric tunability of 92.8% in the maximum field of 10 kV/cm is obtained near 170 °C, and high-tunabilities more than 60% is found in a temperature range between 165 °C and 200 °C in PZN-7%PT. Dielectric tunability above the critical temperature has been discussed within the Landau theory.

KEYWORDS:

• Dielectric tunability
• ferroelectrics
• antiferroelectricas
• tristable states
• phase transition
• Landau theory