Levit Rafael, Martinez-Garcia Julio C, Ochoa Diego A, García José E
Department of Physics, Universitat Politècnica de Catalunya - BarcelonaTech, 08034, Barcelona, Spain.
Group of Nanomaterials and Microsystems, Department of Physics, Universitat Autònoma de Barcelona, 08193, Bellaterra, Spain.
Sci Rep. 2019 Aug 27;9(1):12390. doi: 10.1038/s41598-019-48864-0.
Relaxor ferroelectrics (RF) are outstanding materials owing to their extraordinary dielectric, electromechanical, and electro-optical properties. Although their massive applications, they remain to be one of the most puzzling solid-state materials because understanding their structural local order and relaxation dynamics is being a long-term challenge in materials science. The so-called Vogel-Fulcher-Tamman (VFT) relation has been extensively used to parameterize the relaxation dynamics in RF, although no microscopic description has been firmly established for such empirical relation. Here, we show that VFT equation is not always a proper approach for describing the dielectric relaxation in RF. Based on the Adam-Gibbs model and the Grüneisen temperature index, a more general equation to disentangle the relaxation kinetic is proposed. This approach allows to a new formulation for the configurational entropy leading to a local structural heterogeneity related order parameter for RF. A new pathway to disentangle relaxation phenomena in other relaxor ferroics could have opened.
弛豫铁电体（RF）因其非凡的介电、机电和电光性能而成为杰出的材料。尽管它们有大量应用，但它们仍是最令人困惑的固态材料之一，因为理解其结构局部有序性和弛豫动力学一直是材料科学中的长期挑战。所谓的沃格尔-富尔彻-塔曼（VFT）关系已被广泛用于对RF中的弛豫动力学进行参数化，尽管尚未为这种经验关系建立坚实的微观描述。在这里，我们表明VFT方程并不总是描述RF中介电弛豫的合适方法。基于亚当-吉布斯模型和格律乃森温度指数，提出了一个更通用的方程来解析弛豫动力学。这种方法允许对构型熵进行新的表述，从而得到与RF相关的局部结构非均匀性有序参数。可能已经开辟了一条解析其他弛豫铁电体中弛豫现象的新途径。
