Crystal structure analysis of &lt;i&gt;Ln&lt;/i&gt;&lt;sub&gt;2&lt;/sub&gt;Zr&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;7&lt;/sub&gt; (&lt;i&gt;Ln&lt;/i&gt; = Eu and La) with a pyrochlore composition by high-temperature powder X-ray diffraction

Hagiwara, Takeshi; Nomura, Katsuhiro; Kageyama, Hiroyuki

doi:10.2109/jcersj2.16248

Cited by 17 publications

(5 citation statements)

References 20 publications

(15 reference statements)

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“…S3). The Rietveld refinement for 1.5 ≤ x ≤ 2.0 confirms the clean face-centered-cubic pyrochlore structure with the observation of super-structure peaks 28,29 . This is also anticipated from the closer value of ionic radius ratio (r A /r B ) and position of oxygen atom x(O) in the pyrochlore structure (Fig.…”

Section: Resultssupporting

confidence: 60%

Evolution of spin freezing transition and structural, magnetic phase diagram of Dy$$_{2-\textit{x}}$$La$$_\textit{x}$$Zr$$_{2}$$O$$_{7}$$ (0 $$\le$$ $$\textit{x}$$ $$\le$$ 2.0)

Sheetal

Yadav

2021

Sci Rep

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Dy$$_{2}$$ 2 Zr$$_{2}$$ 2 O$$_{7}$$ 7 a disordered pyrochlore system, exhibits the spin freezing behavior under the application of the magnetic field. We have performed detailed magnetic studies of Dy$$_{2-\textit{x}}$$ 2 - x La$$_\textit{x}$$ x Zr$$_{2}$$ 2 O$$_{7}$$ 7 to understand the evolution of the magnetic spin freezing in the system. Our studies suggest the stabilization of the pyrochlore phase with the substitution of non-magnetic La along with the biphasic mixture of fluorite and pyrochlore phases for the intermediate compositions. We observed that the spin freezing (T$$_{f}$$ f $$\sim$$ ∼ 17 K) at higher La compositions (1.5 $$\le$$ ≤ $$\textit{x}$$ x $$\le$$ ≤ 1.99) is similar to the field-induced spin freezing for low La compositions (0 $$\le$$ ≤ $$\textit{x}$$ x $$\le$$ ≤ 0.5) and the well-known spin ice systems Dy$$_{2}$$ 2 Ti$$_{2}$$ 2 O$$_{7}$$ 7 and Ho$$_{2}$$ 2 Ti$$_{2}$$ 2 O$$_{7}$$ 7 . The low-temperature magnetic state for higher La compositions (1.5 $$\le$$ ≤ $$\textit{x}$$ x $$\le$$ ≤ 1.99) culminates into a spin-glass like state below 6 K. Cole–Cole plot and Casimir-du Pr$$\acute{e}$$ e ´ fit shows the narrow distribution of spin relaxation time in these compounds.

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Section: Resultssupporting

confidence: 60%

Evolution of spin freezing transition and structural, magnetic phase diagram of Dy$$_{2-\textit{x}}$$La$$_\textit{x}$$Zr$$_{2}$$O$$_{7}$$ (0 $$\le$$ $$\textit{x}$$ $$\le$$ 2.0)

Sheetal

Yadav

2021

Sci Rep

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“…Lanthanide zirconates Ln 2 Zr 2 O 7 that adopt the pyrochlore structure exhibit a wide range of chemical and physical properties of interest for fundamental science and with important technological applications. − Some of these properties are significantly altered by structural defects and disorder, which can be easily induced by temperature, pressure, or irradiation. Therefore, intense research efforts are still aimed toward identifying and understanding the prevailing ordering/disordering mechanisms in the pyrochlore structure, as well as to elucidate short- versus long-range structural properties. − In this context, there is a long-standing discussion in the literature as to whether the order–disorder processes are driven by anions, cations, or by both simultaneously. − Despite the substantial amount of experimental work completed by the scientific community, a complete understanding of the fundamental aspects controlling defect formation and annihilation remains elusive. − The present contribution addresses this issue by analyzing the effect of doping and processing conditions on the structural and microstructural features of bulk gadolinium zirconate powders Gd 2 Zr 2 O 7 (GZO). These results are discussed in the context of the existing criteria for predicting the formation and stability of pyrochlore oxides of different compositions.…”

Section: Introductionmentioning

confidence: 99%

A Critical Review of Existing Criteria for the Prediction of Pyrochlore Formation and Stability

Fuentes

Montemayor²,

Mączka

et al. 2018

Inorg. Chem.

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Depending on intrinsic (e.g., radius ratio rule r/ r) and extrinsic factors (e.g., processing conditions), pyrochlore-type LnZrO oxides achieve variable degrees of structural disorder. We report on a systematic study of the structural and microstructural characteristics of the GdLn ZrO system, exploring the effect of replacing Gd with a wide range of homovalent lanthanide ions (Ln = Nd, Sm, Dy, Ho, Y, and Er; x = 0.20 and 0.80). All compositions were prepared via a mechanochemical reaction between the corresponding oxides and characterized by X-ray diffraction (standard and synchrotron sources) using the Rietveld method, as well as by Raman spectroscopy. Irrespective of chemical composition, this study reveals that all compositions exhibit a fluorite-like structure. Furthermore, by firing each sample at 800 and 1400 °C, we are able to analyze the transition to pyrochlore-like structures, featuring different degrees of disorder, in all but GdYZrO, which retains the fluorite structure even after heating. The structural data are used to assess the existing criteria for predicting the formation and stability of the pyrochlore structure; according to this analysis, the simple radius ratio rule ( r/ r), provides a useful and sufficiently robust criterion. Because the pyrochlore structure has a strong tendency to disorder, it is not possible to define an empirical index similar to the Goldschmidt tolerance factor for perovskite.

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“…This indicates the occurrence of several competing processes at temperatures above 700 • C. One of the side processes can be a change in the number of oxygen vacancies, for example, during reaction (2). However, Hagiwara et al [66] showed by XRD that the occupancy of the O(8a) position in Eu 2 Zr 2 O 7 at 900 • C is even less than that at room temperature. Shehu [67] also showed by ND method a slight decrease in the occupancy of the O(8a) position at a temperature of 800 • C relative to room temperature for Nd 2−x Ca x Zr 2 O 7−δ .…”

Section: Total Conductivity and Defects Equilibriummentioning

confidence: 98%

“…In fact, the O(8a) site in the pyrochlore structure is often called interstitial, although this is not exactly like that. This position is free in ideal pyrochlore, for example in La 2 Zr 2 O 7 [66]. With a decrease in the ionic radius of the lanthanide, the probability of the formation of a split oxygen vacancy increases, when the oxygen atom is displaced from the O(48f) site towards the O(8a) site, and as a result, the interstitial oxygen atom is between two vacancies in the O(48f) sites [22].…”

Section: Total Conductivity and Defects Equilibriummentioning

confidence: 99%

Equilibrium of intrinsic and impurity point defects in Ca-doped Sm2Zr2O7

Vorotnikov,

Belyakov,

Ivanov

et al. 2024

Nanosystems: Phys. Chem. Math.

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In this work, a doping strategy was used to achieve a good conductivity in samarium zirconate which crystallizes in the pyrochlore. The production of nanopowders made it possible to form high-density ceramics with an optimal microstructure.It is shown that intrinsic and impurity defects coexist in Sm 2−x Ca x Zr 2 O 7−δ , impairing ion transport at high doping levels. Despite this, Sm 1.95 Ca 0.05 Zr 2 O 7−δ maintains low activation energy of the parent and has good ionic conductivity (10 −3 S•cm −1 at 600 • C) which is one of the largest among oxide pyrochlores. It has been shown to have a good chemical stability. The material has a thermal expansion coefficient (TEC) of 12 ppm K −1 which is higher than YSZ and provides better compatibility with electrode materials. The above makes it possible to successfully use it as a highly stable oxygen electrolyte or an intermediate thin layer at the electrolyte-electrode interface in electrochemical devices.

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Crystal structure analysis of <i>Ln</i><sub>2</sub>Zr<sub>2</sub>O<sub>7</sub> (<i>Ln</i> = Eu and La) with a pyrochlore composition by high-temperature powder X-ray diffraction

Cited by 17 publications

References 20 publications

Evolution of spin freezing transition and structural, magnetic phase diagram of Dy$$_{2-\textit{x}}$$La$$_\textit{x}$$Zr$$_{2}$$O$$_{7}$$ (0 $$\le$$ $$\textit{x}$$ $$\le$$ 2.0)

Evolution of spin freezing transition and structural, magnetic phase diagram of Dy$$_{2-\textit{x}}$$La$$_\textit{x}$$Zr$$_{2}$$O$$_{7}$$ (0 $$\le$$ $$\textit{x}$$ $$\le$$ 2.0)

A Critical Review of Existing Criteria for the Prediction of Pyrochlore Formation and Stability

Equilibrium of intrinsic and impurity point defects in Ca-doped Sm2Zr2O7

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Crystal structure analysis of <i>Ln</i><sub>2</sub>Zr<sub>2</sub>O<sub>7</sub> (<i>Ln</i> = Eu and La) with a pyrochlore composition by high-temperature powder X-ray diffraction

Cited by 17 publications

References 20 publications

Evolution﻿ of spin freezing transition and structural, magnetic phase diagram of Dy$$_{2-\textit{x}}$$La$$_\textit{x}$$Zr$$_{2}$$O$$_{7}$$ (0 $$\le$$ $$\textit{x}$$ $$\le$$ 2.0)

Evolution﻿ of spin freezing transition and structural, magnetic phase diagram of Dy$$_{2-\textit{x}}$$La$$_\textit{x}$$Zr$$_{2}$$O$$_{7}$$ (0 $$\le$$ $$\textit{x}$$ $$\le$$ 2.0)

A Critical Review of Existing Criteria for the Prediction of Pyrochlore Formation and Stability

Equilibrium of intrinsic and impurity point defects in Ca-doped Sm2Zr2O7

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Evolution of spin freezing transition and structural, magnetic phase diagram of Dy$$_{2-\textit{x}}$$La$$_\textit{x}$$Zr$$_{2}$$O$$_{7}$$ (0 $$\le$$ $$\textit{x}$$ $$\le$$ 2.0)

Evolution of spin freezing transition and structural, magnetic phase diagram of Dy$$_{2-\textit{x}}$$La$$_\textit{x}$$Zr$$_{2}$$O$$_{7}$$ (0 $$\le$$ $$\textit{x}$$ $$\le$$ 2.0)