Thermodynamic properties of, and fergusonite-to-scheelite phase transition in, gadolinium orthoniobate GdNbO4 ceramics

Кондратьева, Ольга Николаевна; Никифорова, Г. Е.; Tyurin, A. V.; Хорошилов, А.; Gurevich, V. M.; Гавричев, К. С.

doi:10.1016/j.jallcom.2018.11.272

Cited by 20 publications

(10 citation statements)

References 34 publications

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“…The average ionic radius is the weighted average of the Shannon 18 ionic radii of ions occupying the A-sublattice, assuming that each of them has the same coordination number (CN = 8). The unit cell volume, the a, b, and c parameters, and the monoclinic angle of the undoped multicomponent orthoniobate agree very well with the corresponding average values for the LaNbO 4 , 19 NdNbO 4 , 20 SmNbO 4 , 21 GdNbO 4 , 22 and EuNbO 4 . 23 With increasing calcium content, the average A ion radius increases as Ca 2+ ionic radius for CN = 8 is 1.12 Å, 18 but the unit cell volumes of the oxides containing calcium are lower than that of the undoped one.…”

Section: Crystal Structuresupporting

confidence: 71%

“…Transition temperatures vary from 676°C to 695°C. The transition temperature of La 0.2 Nd 0.2 Sm 0.2 Gd 0.2 Eu 0.2 NbO 4− δ is lower than the average value (712°C) of transition temperatures for LaNbO 4 (500°C 3 ), NdNbO 4 (650°C), SmNbO 4 (775°C 30 ), GdNbO 4 (805°C 22 ), and EuNbO 4 (830°C 30 ). The presence of calcium weakly influences the transition temperature.…”

Section: Resultsmentioning

confidence: 64%

“… Note : For comparison, the unit cell parameters obtained as an average of the parameters of La 19 , Nd 20 , Sm 21 , Gd 22 , and EuNbO 4 23 are shown (marked with an asterisk).…”

Section: Resultsmentioning

confidence: 99%

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Enhanced acceptor concentration, proton conductivity, and hydration in multicomponent rare‐earth ortho‐niobates

Dawczak,

Skubida,

Mielewczyk‐Gryń

et al. 2023

J Am Ceram Soc.

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The structural properties of (La0.2Nd0.2Sm0.2Gd0.2Eu0.2)1‐xCaxNbO4‐δ (x = 0 ‐ 0.05) series have been studied by X‐ray powder diffraction at room temperature. The thermal properties were investigated using thermogravimetry, from which the concentration of proton defects was determined. Additionally, dilatometry studies were carried out, from which the thermal expansion coefficients and the phase transition temperature between low‐ and high‐temperature polymorphs were determined. In order to determine the electrical properties, the electrochemical impedance spectroscopy measurements under atmospheres of dry synthetic air and saturated with water vapor and heavy water at 300 ‐ 800°C temperature range were performed. All the studied materials were single‐phase compositions and were stable in monoclinic I2/c crystal structure at room temperature. The water uptake studies revealed a small mass change under the switch from dry to humidified synthetic air atmospheres, suggesting the formation of proton defects. The phase transition from monoclinic to tetragonal crystal structure in the (La0.2Nd0.2Sm0.2Gd0.2Eu0.2)1‐xCaxNbO4‐δ (x = 0 ‐ 0.05) series occurs above 650°C. A small amount of calcium dopant increases the total conductivity in all tested atmospheres by two orders of magnitude, for example, from 0.34 μScm−1 in La0.2Nd0.2Sm0.2Gd0.2Eu0.2NbO4 to 63.7 μScm−1 in (La0.2Nd0.2Sm0.2Gd0.2Eu0.2)0.95Ca0.05NbO4‐δ at 700°C in humid synthetic air atmosphere.This article is protected by copyright. All rights reserved

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Section: Crystal Structuresupporting

confidence: 71%

Section: Resultsmentioning

confidence: 64%

See 1 more Smart Citation

Enhanced acceptor concentration, proton conductivity, and hydration in multicomponent rare‐earth ortho‐niobates

Dawczak,

Skubida,

Mielewczyk‐Gryń

et al. 2023

J Am Ceram Soc.

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“…), and obtain the phase transition information and the nature of the interaction between atoms, and calculate the phonon state density and determine the zero‐point energy. [ 13–20 ]…”

Section: Introductionmentioning

confidence: 99%

“…), and obtain the phase transition information and the nature of the interaction between atoms, and calculate the phonon state density and determine the zero-point energy. [13][14][15][16][17][18][19][20] Infrared spectroscopy and Raman spectroscopy (Raman) are the two important tools to characterize materials. Meanwhile, the optically active vibrational modes are the basic and necessary data for identifying crystal structure and molecular structures.…”

mentioning

confidence: 99%

The Structural, Lattice Dynamic, Thermodynamic, and Mechanical Characterization of Na₂Mo₂O₇ Crystal by First‐Principles

Gao

Zhang

et al. 2022

Physica Status Solidi (b)

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The structural, electronic, lattice dynamic, thermodynamic, and mechanical properties of disodium dimolybdate (Na2Mo2O7) are studied using first‐principles. First, for the crystal structure, the calculated structural parameters have a standard deviation of less than 1.7% compared with the experimental results. Then, the calculated electronic energy band and density of states reveal that Na2Mo2O7 is an insulator and its bandgap is about 2.87 eV. In addition, the linear response method is used to study the lattice dynamics, and the complete phonon dispersion curve, infrared spectra, Raman shift, Born effective charge, and longitudinal optical–transverse optical (LO–TO) splitting characteristic for Na2Mo2O7 are presented for the first time; its thermodynamic properties are worked out based on the phonon density of states (PDOS). Furthermore, the result of elastic anisotropy shows the title compound is a highly anisotropic material. The calculation results in this article are conducive to the development of Na2Mo2O7 and provide guidelines for further experimental research to a certain extent.

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Shape-Memory Materials

Behera

2021

Advanced Materials

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Thermodynamic properties of, and fergusonite-to-scheelite phase transition in, gadolinium orthoniobate GdNbO4 ceramics

Cited by 20 publications

References 34 publications

Enhanced acceptor concentration, proton conductivity, and hydration in multicomponent rare‐earth ortho‐niobates

Enhanced acceptor concentration, proton conductivity, and hydration in multicomponent rare‐earth ortho‐niobates

The Structural, Lattice Dynamic, Thermodynamic, and Mechanical Characterization of Na₂Mo₂O₇ Crystal by First‐Principles

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Thermodynamic properties of, and fergusonite-to-scheelite phase transition in, gadolinium orthoniobate GdNbO4 ceramics

Cited by 20 publications

References 34 publications

Enhanced acceptor concentration, proton conductivity, and hydration in multicomponent rare‐earth ortho‐niobates

Enhanced acceptor concentration, proton conductivity, and hydration in multicomponent rare‐earth ortho‐niobates

The Structural, Lattice Dynamic, Thermodynamic, and Mechanical Characterization of Na2Mo2O7 Crystal by First‐Principles

Shape-Memory Materials

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Product

Resources

About

The Structural, Lattice Dynamic, Thermodynamic, and Mechanical Characterization of Na₂Mo₂O₇ Crystal by First‐Principles