Sm_2−xDy_xZr₂O₇ Pyrochlores: Probing Order−Disorder Dynamics and Multifunctionality

Abstract

The present work involves the synthesis of a series of Sm(2-x)Dy(x)Zr(2)O(7) compounds (0.0 ≤ x ≤ 2.0) by a controlled gel combustion process. The powders were thoroughly analyzed by powder X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy, and diffuse-reflectance UV-visible spectroscopy. The powder XRD studies revealed the system to be single-phasic throughout with retention of pyrochlore-type ordering until 40 mol % of Dy(3+), beyond which the pyrochlore lattice gives way to the defect fluorite structure. Interestingly, Raman spectroscopic studies (as against XRD studies) showed retention of pyrochlore-type ordering throughout the homogeneity range of the compositions studied. This is perhaps the first study that reports retention of a weak pyrochlore-type superstructure in the Dy(2)Zr(2)O(7) system, which was otherwise known to crystallize in the defect fluorite system. The ionic conductivity measurements showed an increase in the activation energy (E(a)) with an increase in the mole percent of Dy(3+) owing to the decreased mobility with an increase in the degree of disorder. The system possesses a tunable band gap with varying amounts of Dy(3+). First-principles calculations were performed to support a decrease in the band gap of the doped system with an increase in the Dy(3+) content. The potential as photocatalysts of some of these compositions was explored, and they exhibited high photocatalytic activity for degradation of xylenol orange, with t(1/2) increasing from pure Sm(2)Zr(2)O(7) to pure Dy(2)Zr(2)O(7).

Influence of Sm3+ doping on microstructure and electrical properties of ((Nd0.7Yb0.3)1-xSmx)2Zr2O7

“…The increase in the order degree of cations facilitates the ordering of oxygen ions in long range instead of short range. It also reveals that the ordering of anions is later than the ordering of cations, which is consistent with previous results by Farheen et al [17][18][19] Thus a conclusion can be made that as the structure of this system changing from defect fluorite to pyrochlore, the oxygen anions are merely becoming long-range ordered, while the short range degree of oxygen ions remains unchanged. The ordering of this material is mainly due to the ordering of cations, but not the ordering of oxygen ions in micro domains.…”

Effect of fluorite phase on the electrical conductivity of (Sm1−Dy )2Zr2O7 pyrochlore

“…Therefore, we have adopted the solid solutions of Sm 2 Zr 2 O 7 pyrochlore and Dy 2 Zr 2 O 7 fluorite, described as x = 0 to 1.0 in (Sm 1 − x Dy x ) 2 Zr 2 O 7 to clarify the relationship between the crystal structure and electrical conductivity. Recently, an analogous research on the order-disorder dynamics of Sm 2 − x Dy x Zr 2 O 7 has been published [9][10][11]. Here, we will present new results on the effect of the fluorite phase on the electrical conductivity of the pyrochlore and the grain boundary effect by Al 2 O 3 addition.…”

“…8. Each spectrum of all the samples was composed of four well-defined bands corresponding to characteristics of pyrochlore type structure [11,14]. As the amount of Dy content increased, these four peaks broadened considerably and the spectrum for x = 0.4 was clearly different from other spectra concerning with the shapes of these peaks and relative intensities.…”

Influence of Cation Substitution and Activator Site Exchange on the Photoluminescence Properties of Eu3+-Doped Quaternary Pyrochlore Oxides

“…All other modes are related to 48f site oxygen anion. 48 The other highfrequency modes may be due to combination bands or overtones. 35 Exchange interaction between Eu 3+ is of great probability for compounds having Eu separation below 5 Å.…”