Local Structure and Order-Disorder Transitions in "Empty" Ferroelectric Tetragonal Tungsten Bronzes
Local Structure and Order-Disorder Transitions in "Empty" Ferroelectric Tetragonal Tungsten Bronzes
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DOI：
10.1021/acs.chemmater.0c02639
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发表时间：
2020-10-13
影响因子：
8.6
通讯作者：
Morrison, Finlay D.
中科院分区：
文献类型：
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作者：
McNulty, Jason A.;Pesquera, David;Morrison, Finlay D.
“空的”四方钨青铜Ba4La0.67矩形1.33Nb10O30显示作为温度的函数的弛豫样和正常介电异常;前者与铁电性的损失相关，并且被提出源于阴离子无序[Chem. Mater. 2016，28，4616-4627]。在这里，我们提出了总中子散射和对分布函数（PDF）分析，这表明在弛豫过渡的氧-氧距离的分布增加，并支持建议的阴离子无序机制。无序化过程可以通过降低平均A-阳离子尺寸（即，Nd掺杂：Ba-4（La 1-xNdx）（0.67）Nb 10 O30）;这引入了与先前报道的晶体化学框架模型一致的更强传播的倾斜系统[Chem.Mater. 2015，27，3250-3261]。使用共振超声光谱获得的机械损耗数据也表明随着Nd取代的增加，无序过程不稳定。
The "empty" tetragonal tungsten bronze Ba4La0.67 rectangle 1.33Nb10O30 displays both relaxor-like and normal dielectric anomalies as a function of temperature; the former is associated with loss of ferroelectricity and was proposed to originate from anion disordering [Chem. Mater. 2016, 28, 4616-4627]. Here we present total neutron scattering and pair distribution function (PDF) analysis, which shows an increase in the distribution of oxygen-oxygen distances at the relaxor transition and which supports the proposed anion disordering mechanism. The disordering process can be destabilized by reducing the average A-cation size (i.e., Nd-doping: Ba-4(La1-xNdx)(0.67)Nb10O30); this introduces a more strongly propagating tilt system in line with the previously reported crystal-chemical framework model [Chem. Mater. 2015, 27, 3250-3261]. Mechanical loss data obtained using resonant ultrasound spectroscopy also indicate destabilization of the disordering process with increasing Nd-substitution.