Correlation of dynamical disorder and oxy-ion diffusion mechanism in a Dy, W co-doped La2Mo2O9 system: an electrolyte for IT-SOFCs,Dalton Transactions

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Correlation of dynamical disorder and oxy-ion diffusion mechanism in a Dy, W co-doped La2Mo2O9 system: an electrolyte for IT-SOFCs
Dalton Transactions ( IF 3.5 ) Pub Date : 2020-08-26 , DOI: 10.1039/d0dt02954h
Ruhi Naz Nayyer _{1,

2,

3,

4,

5} , Shyamkant Anwane _{1,

5,

6,

7} , Vishwajit Gaikwad _{1,

5,

8,

9} , Vasant Sathe _{5,

10,

11,

12} , Smita Acharya _{1,

2,

3,

4,

5}

Affiliation

In the present attempt, a Dy, W co-doped La₂Mo₂O₉ (LMX) system is explored to understand the order–disorder phase transition, dynamical disorder state and their influence on the oxy-ion diffusion mechanism. The X-ray diffraction study confirms the co-dopant induced suppression of the order–disorder phase transition temperature of LMX. The oxygen ion diffusion in the LMX matrix is through intrinsic oxygen vacancies. Disorder oxygen vacancies enhance the degree of freedom of oxy-ion diffusion; these are related to the dynamical disorder states in LMX. These disorder states are demonstrated by high temperature Raman spectra. Dynamical disordering of oxygen vacancies in co-doped LMX systems is revealed by studying the rate of change of intensity of the Mo–O bond vibration as a function of temperature; non-uniformity in the rate of change of intensity is correlated to dynamical disorder. The dielectric relaxation studied by using dielectric loss spectra reveals a single relaxation peak for the pure-LMX system, while two dielectric relaxation peaks are revealed for doped LMX systems. Oxygen vacancy reorientation associated with dielectric relaxation is correlated to the diffusion process between O(1) → O(2) and O(1) → O(3) oxygen ion-vacancy exchange sites in doped LMX systems, while it is O(1) through orderly arranged oxygen vacancies in the pure LMX system. To ascertain the relaxation dynamics of the bulk system, electric modulus formalism is helpful, M′′ data are fit by the Bergman function represented by the Kohlrausch–Williams–Watts (KWW) formula and non-Debye type relaxation is revealed for all systems. The activation energy of oxy-ion diffusion is reduced by a co-doping effect. Ionic conductivity extracted from complex impedance spectra indicates that oxy-ion conductivity in a co-doped LMX system is improved almost one order as compared to the pure system. The study reveals that a co-doped LMX system has the potential to be used as electrolytes for intermediate temperature solid oxide fuel cells (400–700 °C, IT-SOFCs).

中文翻译：

Dy，W共掺杂La2Mo2O9系统中动力紊乱与氧离子扩散机理的相关性：IT-SOFC的电解质

在目前的尝试中，Dy，W共掺杂了La ₂ Mo ₂ O ₉探索（LMX）系统以了解有序-无序相变，动力学无序状态及其对氧离子扩散机理的影响。X射线衍射研究证实了共掺杂物对LMX有序-无序相变温度的抑制作用。LMX基质中的氧离子扩散是通过固有的氧空位实现的。无序的氧空位提高了氧离子扩散的自由度；这些与LMX中的动态障碍状态有关。这些无序状态通过高温拉曼光谱证明。通过研究Mo-O键振动强度随温度变化的速率，揭示了共掺杂LMX系统中氧空位的动态无序。强度变化率的不均匀与动力障碍有关。通过使用介电损耗谱研究的介电弛豫揭示了纯LMX系统的一个弛豫峰，而对于掺杂LMX系统则揭示了两个介电弛豫峰。与介电弛豫相关的氧空位重新定向与掺杂LMX系统中O（1）→O（2）和O（1）→O（3）氧离子空位交换位点之间的扩散过程相关，而为O（1 ）通过纯LMX系统中有序排列的氧空位。为了确定整体系统的弛豫动力学，电子模量形式主义是有帮助的，与介电弛豫相关的氧空位重新定向与掺杂LMX系统中O（1）→O（2）和O（1）→O（3）氧离子空位交换位点之间的扩散过程相关，而为O（1 ）通过纯LMX系统中有序排列的氧空位。为了确定整体系统的松弛动力学，电子模量形式主义是有帮助的，与介电弛豫相关的氧空位重新定向与掺杂LMX系统中O（1）→O（2）和O（1）→O（3）氧离子空位交换位点之间的扩散过程相关，而为O（1 ）通过纯LMX系统中有序排列的氧空位。为了确定整体系统的弛豫动力学，电子模量形式主义是有帮助的，M ''数据通过由Kohlrausch–Williams–Watts（KWW）公式表示的Bergman函数拟合，并且对所有系统都显示了非Debye型松弛。共掺杂效应降低了氧离子扩散的活化能。从复数阻抗谱中提取的离子电导率表明，与纯系统相比，共掺杂LMX系统中的氧离子电导率几乎提高了一个数量级。研究表明，共掺杂LMX系统有潜力用作中温固体氧化物燃料电池（400-700°C，IT-SOFC）的电解质。

更新日期：2020-10-06

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