Comparative analysis of long- and short-range structures features in titanates Ln2Ti2O7 and zirconates Ln2Zr2O7 (Ln = Gd, Tb, Dy) upon the crystallization process

Попов, В. В.; Менушенков, А. П.; Иванов, А. А.; Gaynanov, B. R.; Yastrebtsev, А. А.; d’Acapito, Francesco; Puri, Alessandro; Castro, Germán R.; Щетинин, И. В.; Железный, М. В.; Zubavichus, Ya. V.; Понкратов, К.В.

doi:10.1016/j.jpcs.2019.02.019

Cited by 27 publications

(11 citation statements)

References 51 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For the Er 2 Zr 2 O 7 sample, the thermal conducti- vity goes from nearly 1.2 W/mK at 300 K to 0.8 W/mK at 773 K. For the remaining samples, lower values of the thermal conductivity are obtained. Similar results were reported by Jie and collaborators [23], where the decrease in temperature of the thermal conductivity could be associated with the improvement in the efficiency of the thermal barrier coating compounds [23,[24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42]. Figure 7b) shows the values of the thermal conductivity extracted from Fig.…”

Section: Thermolectric Propertiessupporting

confidence: 83%

Electrical and thermal conductivities of rare-earth A2Zr2O7 (A = Pr, Nd, Sm, Gd, and Er)

et al. 2021

View full text Add to dashboard Cite

Structural and thermoelectric properties of rare-earth zirconates A2Zr2O7, with A = Pr, Nd, Sm, Gd, and Er, were studied. Samples were prepared by solid-state reaction at ambient pressure with temperatures between 1000 and 1400 °C. The resulting compounds were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM/EDS). The XRD analyses showed the formation of polycrystalline Pr2Zr2O7, Nd2Zr2O7, Sm2Zr2O7, Gd2Zr2O7 and Er2Zr2O7 phases, with a cubic cell (space group Fm3m) and traces of the raw used materials. The micrographs obtained by SEM show the formation of heterogeneous grains with a size that ranges from 0.7 to 4.7 μm. All A2Zr2O7 samples present porous surfaces. Thermal conductivities were measured at different temperatures, from 300 to 900 K. In most of the samples, the thermal conductivity monotonically decreases with temperature, from 0.40 – 1.17 W/mK at 300 K to 0.27 – 0.77 W/mK at 773.15 K. At a fixed temperature, the thermal conductivity decreases almost monotonically with the ionic radius (IR) of the rare-earth elements (where IR (Er3+) = 0.890 Å < IR (Gd3+) = 0.938 Å < IR (Sm3+) = 0.958 Å < IR (Nd3+) = 0.983 Å < IR (Pr3+) = 0.99 Å).

show abstract

Section: Thermolectric Propertiessupporting

confidence: 83%

Electrical and thermal conductivities of rare-earth A2Zr2O7 (A = Pr, Nd, Sm, Gd, and Er)

et al. 2021

View full text Add to dashboard Cite

show abstract

“…However, the CN of Zr-O decreased significantly when keeping increasing the U content in Nd 2-x U x Zr 2 O 7+ and Nd 2 Zr 2-y U y O 7+ . In this case, more uranium is introduced into pyrochlore, which causes the Zr-O octahedron to be distorted, and the structure has more oxygen disorder characteristics by the movement of O 48f and the formation of anionic Frenkel defects (Popov et al, 2019). In particular, this disorder is maximized at the highest doping concentration, which is consistent with the extremely low characteristic peak of pyrochlore in the Raman results.…”

Section: Local Electronic and Crystal Structuresupporting

confidence: 71%

“…3(c) shows the Zr K-edge XANES spectra of the NZO and U-doped NZO samples, which can be characterized by an obvious pre-edge structure (labelled by a) and a main peak split into two well resolved features (labelled by b and c). Peaks a and b/c correspond to the electronic transition from the 1s to 4d orbital and the dipole-allowed transition from the 1s to 5p orbital, respectively (Komyoji et al, 1992;Popov et al, 2019). These features of all samples are close to those in the pyrochlore phase rather than in the defect-fluorite phase (Nandi et al, 2020).…”

Section: Local Electronic and Crystal Structurementioning

confidence: 84%

Controllable sites and high-capacity immobilization of uranium in Nd₂Zr₂O₇ pyrochlore

Sun

Zhou

et al. 2022

J Synchrotron Radiat

View full text Add to dashboard Cite

As potential nuclear waste host matrices, two series of uranium-doped Nd2Zr2O7 nanoparticles were successfully synthesized using an optimized molten salt method in an air atmosphere. Our combined X-ray diffraction, Raman and X-ray absorption fine-structure (XAFS) spectroscopy studies reveal that uranium ions can precisely substitute the Nd site to form an Nd2–x U x Zr2O7+δ (0 ≤ x ≤ 0.2) system and the Zr site to form an Nd2Zr2–y U y O7+δ (0 ≤ y ≤ 0.4) system without any impurity phase. With increasing U concentration, there is a phase transition from pyrochlore (Fd 3 m) to defect fluorite (Fm 3 m) structures in both series of U-doped Nd2Zr2O7. The XAFS analysis indicates that uranium exists in the form of high-valent U6+ in all samples. To balance the extra charge for substituting Nd3+ or Zr4+ by U6+, additional oxygen is introduced accompanied by a large structural distortion; however, the Nd2Zr1.6U0.4O7+δ sample with high U loading (20 mol%) still maintains a regular fluorite structure, indicating the good solubility of the Nd2Zr2O7 host for uranium. This study is, to the best of our knowledge, the first systematic study on U-incorporated Nd2Zr2O7 synthesized via the molten salt method and provides convincing evidence for the feasibility of accurately immobilizing U at specific sites.

show abstract

“…The rare earth pyrochlore (RE2Ti2O7) titanates are emerging as multi-functional materials because of their unique structural and intriguing physical properties which include magnetism, dielectric and ferroelectric phenomena, and also used as solid state electrolytes [1,2,11,[3][4][5][6][7][8][9][10] . The gadolinium titanate (Gd2Ti2O7, GTO) is one of the technologically important materials with diverse applications including photocatalysis, ionic conductivity, host material for optical emission and nuclear waste immobilization [4][5][6][7][8][9] .…”

Section: Introductionmentioning

confidence: 99%

Raman and Photoluminescence Spectroscopic Studies on Structural Disorder in Oxygen Deficient Gd₂Ti₂O_7‐δ Single Crystals

Suganya

Ganesan

Vijayakumar

et al. 2022

Crystal Research and Technology

View full text Add to dashboard Cite

We report on Raman and photoluminescence spectroscopic studies on oxygen vacancy induced structural disorder in Gd2Ti2O7- single crystals grown by optical floating zone technique under argon atmosphere. The oxygen vacancies in Gd2Ti2O7- wafers decrease with thermal annealing in air atmosphere. The full width at half maximum of X-ray diffraction rocking curve decreases from 245 to 157 arc-second and the optical transmittance increases from 23 to 87 % (at 1000 nm) upon post growth thermal annealing. Raman spectroscopic studies reveal a monotonic increase in intensity of O-Gd-O (Eg) and Ti-O (A1g) stretching modes with thermal annealing.Since these modes are associated with modulation of oxygen x parameter which is sensitive to Ti-O octahedron distortion, the increase in Raman intensity indicates an improvement in structural ordering of oxygen sub-lattice in Gd2Ti2O7-. Moreover, the photoluminescence studies also corroborate the Raman analysis in terms of reduction of structural defects associated with oxygen vacancies as a function of thermal annealing. This study demonstrates the effectiveness of using Raman spectroscopy to probe the structural disorder in Gd2Ti2O7- crystals.

show abstract

Comparative analysis of long- and short-range structures features in titanates Ln2Ti2O7 and zirconates Ln2Zr2O7 (Ln = Gd, Tb, Dy) upon the crystallization process

Cited by 27 publications

References 51 publications

Electrical and thermal conductivities of rare-earth A2Zr2O7 (A = Pr, Nd, Sm, Gd, and Er)

Electrical and thermal conductivities of rare-earth A2Zr2O7 (A = Pr, Nd, Sm, Gd, and Er)

Controllable sites and high-capacity immobilization of uranium in Nd₂Zr₂O₇ pyrochlore

Raman and Photoluminescence Spectroscopic Studies on Structural Disorder in Oxygen Deficient Gd₂Ti₂O_7‐δ Single Crystals

Contact Info

Product

Resources

About

Comparative analysis of long- and short-range structures features in titanates Ln2Ti2O7 and zirconates Ln2Zr2O7 (Ln = Gd, Tb, Dy) upon the crystallization process

Cited by 27 publications

References 51 publications

Electrical and thermal conductivities of rare-earth A2Zr2O7 (A = Pr, Nd, Sm, Gd, and Er)

Electrical and thermal conductivities of rare-earth A2Zr2O7 (A = Pr, Nd, Sm, Gd, and Er)

Controllable sites and high-capacity immobilization of uranium in Nd2Zr2O7 pyrochlore

Raman and Photoluminescence Spectroscopic Studies on Structural Disorder in Oxygen Deficient Gd2Ti2O7‐δ Single Crystals

Contact Info

Product

Resources

About

Controllable sites and high-capacity immobilization of uranium in Nd₂Zr₂O₇ pyrochlore

Raman and Photoluminescence Spectroscopic Studies on Structural Disorder in Oxygen Deficient Gd₂Ti₂O_7‐δ Single Crystals