Połomska Maria, Hilczer Bożena, Markiewicz Ewa, Trybuła Zbigniew, Andrzejewski Bartłomiej, Szafraniak-Wiza Izabela, Pietraszko Adam
IEEE Trans Ultrason Ferroelectr Freq Control. 2013 Aug;60(8):1603-11. doi: 10.1109/TUFFC.2013.2741.
Cd(2)Nb(2)O(7) is still an interesting ferroelectric material because of its high permittivity value at helium temperatures and a variety of dielectric relaxation processes, the origin of which is still puzzling. We prepared hot-pressed ceramics, with grain sizes from 100 to 150 nm, obtained from Cd(2)Nb(2)O(7) nanopowders synthesized by high-energy milling of CdO and Nb(2)O(5) and studied their dielectric response and thermal properties. The nanoceramics were characterized by X-ray diffraction and their dielectric properties were measured at temperatures from 4K to 575K. Dielectric response of the nanoceramics was found to consist of a huge anomaly at ~150K with complex dielectric absorption and three relaxation processes apparent in frequency and temperature dependences of the imaginary part of permittivity in the temperature range from 18K to 145K. The anomaly at ~150K is related to overlapping contributions from the Curie point (shifted downward because of the size effect) and a dielectric relaxation process. The behavior of three relaxation modes observed at temperatures below 145K is discussed, based on the model proposed by Malcherek of polar nanoregions in the orthorhombic phase of Cd(2)Nb(2)O(7) and the theory of dielectric response of ferroelectric relaxors by Bokov and Ye.
Cd(2)Nb(2)O(7)仍然是一种有趣的铁电材料，因为它在氦温度下具有高介电常数，并且存在各种介电弛豫过程，其起源仍然令人困惑。我们制备了热压陶瓷，其晶粒尺寸为100至150纳米，由通过高能球磨CdO和Nb(2)O(5)合成的Cd(2)Nb(2)O(7)纳米粉末制成，并研究了它们的介电响应和热性能。通过X射线衍射对纳米陶瓷进行了表征，并在4K至575K的温度下测量了它们的介电性能。发现纳米陶瓷的介电响应在约150K处存在巨大异常，伴有复杂的介电吸收，并且在18K至145K的温度范围内，介电常数虚部的频率和温度依赖性中明显出现三个弛豫过程。约150K处的异常与居里点（由于尺寸效应而向下移动）和介电弛豫过程的重叠贡献有关。基于Malcherek提出的关于Cd(2)Nb(2)O(7)正交相中的极性纳米区域的模型以及Bokov和Ye提出的铁电弛豫体的介电响应理论，讨论了在低于145K的温度下观察到的三种弛豫模式的行为。
