四方晶系
铁电性
钨
人工智能
材料科学
物理
计算机科学
相(物质)
冶金
光电子学
量子力学
电介质
作者
E. Buixaderas,Šarūnas Svirskas,Christelle Kadlec,M. Savinov,Patricija Lapienytė,K. R. Anirudh,Cosme Milesi-Brault,D. Nuzhnyy,J. Dec
出处
期刊:Physical review
日期:2024-09-03
卷期号:110 (10)
标识
DOI:10.1103/physrevb.110.104302
摘要
Using a broadband dielectric spectroscopy approach (1 to ${10}^{14}$ Hz) we prove that the tungsten bronze $\mathrm{C}{\mathrm{a}}_{0.3}\mathrm{B}{\mathrm{a}}_{0.7}\mathrm{N}{\mathrm{b}}_{2}{\mathrm{O}}_{6}$ (CBN-30) displays a ferroelectric phase transition of mixed displacive and order-disorder character, and its paraelectric phase does not show traces of relaxor behavior but precursor effects as polar fluctuations below about 550 K. The analysis of the submegahertz dielectric response, together with infrared and Raman spectroscopy, reveals that simultaneous polarization mechanisms are responsible for the phase transition. The comparison of the excitations found in CBN-30 with those of (Sr,Ba)$\mathrm{N}{\mathrm{b}}_{2}{\mathrm{O}}_{6}$ reveals that these mechanisms are congruous, although in CBN-30 the main relaxation process behaves differently due to the different domain structure. The excitations are phenomenologically assigned to phonons, to an anharmonic vibration of cationic origin which plays the role of a soft central mode (${\ensuremath{\nu}}_{\mathrm{THz}}$), and to a relaxation in the gigahertz range (${\ensuremath{\nu}}_{01}$), probably due to polarization fluctuations of nanometric size which carry the main part of the permittivity and split below ${T}_{\mathrm{C}}$ into several weaker excitations with different polarization correlation lengths. The overall dielectric response is therefore explained by the coexistence of several excitations with different thermal behaviors, corroborating the complexity of the tetragonal tungsten bronze structures.
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