Sr2(Mg1−Ga )Ge2O7+0.5: Melilite-type oxygen ionic conductor associated with fivefold coordinated germanium and gallium

Park, Hee Jung; Kim, Tae-Gon; Kwak, Chan; Jung, Doh Won; Lee, Sang-Mock; Lee, Kyu Hyoung

doi:10.1016/j.jpowsour.2014.11.088

Cited by 8 publications

(5 citation statements)

References 23 publications

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“…The interstitial oxide ions are located nearly at the centers of some of the five-membered rings and coordinated up and down by two A/B cations and by the Ga 3+ ions within the tetrahedral layer [14,15]. Such a coordination structure can be stabilized by the distortion of the [GaO 4 ] tetrahedra and the formation of [GaO 5 ] polyhedron [16,17]. The cooperative migration mechanism involving the concerted knock-on motion of the interstitial oxide ions and lattice oxide ions along certain directions in the two-dimensional tetrahedral layers was revealed by molecular dynamics (MD) simulations [18] and supported by density functional theory (DFT) calculation and Kinetic Monte Carlo simulations [19], which leads to the significant anisotropy of oxide ion conductivity in the melilite structured oxides [20].…”

Section: Introduction mentioning

confidence: 99%

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Sol—gel approach to low-temperature synthesis of single-phase metastable La2Ga3O7.5 melilite with enhanced grain-boundary oxide ionic conductivity via a kinetically favorable mechanism

Zhang

Zhao²,

Ye³

et al. 2022

J Adv Ceram

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Starting with the stoichiometric and highly homogeneous gel-precursor, single-phase metastable melilite La2Ga3O7.5, as the end-member of solid solution La1+xSr1−xGa3O7+x/2 (0≼x≼1), has been synthesized by solid-state reaction at 700 °C for 2 h via a kinetically favorable mechanism and characterized by X-ray diffraction (XRD), Raman, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), AC impedance spectroscopy, etc. It has been revealed that the as-synthesized melilite La2Ga3O7.5 shows an orthorhombic symmetry with crystal cell parameters a = 11.4690(1) Å, b = 11.2825(4) Å, and c = 10.3735(4) Å, while has more Raman active modes than LaSrGa3O7 with a tetragonal structure, which was also synthesized under the same conditions for comparison, but tends to slowly decompose into perovskite LaGaO3 and Ga2O3 when annealed at 700 °C for over 20 h driven by its meta-stability. Moreover, the metastable La2Ga3O7.5 shows a higher XPS binding energy for the excess oxide ions in the crystal structure than those at normal lattice sites. Its intrinsic grain oxide ion conductivity can reach as high as 0.04 and 0.51 mS·cm−1 at 550 and 700 °C, respectively, characterized by a simple Arrhenius relationship ln(σT)—1/T with invariable activation energy, Ea = 1.22 eV, over the temperature range from 300 to 700 °C, along with an apparent grain boundary conductivity that is about double that from the grains thanks to the clean grain boundaries. This paper provides a new strategic approach to the synthesis of complex oxides that may be of high performance but are difficultly achieved by the conventional ceramic method at high temperatures.

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Section: Introduction mentioning

confidence: 99%

“…Among the melilite oxide electrolytes [13,15,17,[21][22][23][24][25], La 1+x M 1−x Ga 3 O 7+0.5x (M = Ca, Sr, and Ba) [13,21,22] are the most representative ones. The La 1+x Ca 1−x Ga 3 O 7+0.5x system has a tetragonal symmetric structure when 0 ≤ x ≤ 0.54, and shows an orthorhombic symmetry when 0.55 < x ≤ 0.64.…”

Section: Introduction mentioning

confidence: 99%

Sol—gel approach to low-temperature synthesis of single-phase metastable La2Ga3O7.5 melilite with enhanced grain-boundary oxide ionic conductivity via a kinetically favorable mechanism

Zhang

Zhao²,

Ye³

et al. 2022

J Adv Ceram

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“…x Ga 3 O 7 + 0.5x melilite has attracted considerable attention since 2008. [18][19][20][21][22] The discovery of interstitial oxide ion conduction in the melilite structure and its original mechanism for the interstitial oxide ion conduction have offered new clues to search for innovative oxide ion conductors. These developments have thus stimulated the exploration of new melilite interstitial oxide ion conductors and in-depth understanding of their interstitial oxygen migration mechanisms.…”

Section: Introductionmentioning

confidence: 99%

“…Its oxide ion conductivity is higher than that of traditional fluorite‐type Y‐stabilized zirconia (YSZ) electrolytes (0.03–0.13 S/cm over the 800–1000 °C temperature range), and essentially equivalent to that of Gd‐doped cerium (GDC) oxide material (0.046 S/cm at the 700 °C temperature) . The identification of interstitial oxide ion conduction in La 1+ x Sr 1– x Ga 3 O 7+0.5 x melilite has attracted considerable attention since 2008 …”

Section: Introductionmentioning

confidence: 99%

Development of Melilite‐Type Oxide Ion Conductors

Zhou

Allix

et al. 2020

The Chemical Record

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Lowering the operating temperature of solid oxide fuel cells (SOFCs) requires high performance oxide ion conductor electrolytes. Recently tetrahedra-based structures have been attracting considerable attention for oxide ion conductor development, among which the layered tetrahedral network melilite structure appears particularly interesting owing to its remarkable capability to accommodate and transport interstitial oxide ions, compared with isolated tetrahedral anion structures. Stabilization and migration mechanisms of interstitial oxide ions in melilites have been systematically investigated using local structural relaxation from both electrostatic Coulomb interaction and chemical bonding aspects based on atomic and electronic structures respectively using experimental and theoretical approaches. These reveal cationic size and chemical bonding effects on stabilization and migration mechanisms of interstitial oxide ions. Lately, full crystallization from glass, an innovative synthesis method, was employed to produce new metastable melilite oxide ion conductors which are inaccessible using classic solid state reaction owing to cationic size effect. Finally, the thermal and chemical stability at low temperature and the high oxide ion conductivity of the best melilite oxide ion conductors based on LaSrGa 3 O 7 are likely to provide real possibilities of applications of melilite-type electrolytes in SOFCs and other related devices.

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“…Since the 1990s, compounds with melilite structure have been intensively studied due to their interesting electrochemical [1], magnetic [2–4], luminescence [5–7] and structural properties [8–10]. The melilites are a large family of materials with the general formula [8] A 2 [4] B [4] C 2 O 7 where A is a large cation such as Ca, Sr, Ba, Na, K, Y, lanthanides, Pb or Bi; B is a small cation such as Al, Be, Co, Cu, Cd, Fe, Ga or Mg; and finally C = Si, B, Al, Cr, Ge or V. The number in square brackets [ N ] indicates the coordination number (CN) of the element.…”

Section: Introductionmentioning

confidence: 99%

Crystallization and visible–near-infrared luminescence of Bi-doped gehlenite glass

et al. 2018

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Gehlenite glass microspheres, doped with a different concentration of Bi3+ ions (0.5, 1, 3 mol%), were prepared by a combination of solid-state reaction followed by flame synthesis. The prepared glass microspheres were characterized from the point of view of surface morphology, phase composition, thermal and photoluminescence (PL) properties by optical and scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and PL spectroscopy. The closer inspection of glass microsphere surface by SEM confirmed a smooth surface. This was further verified by XRD. The basic thermal characteristics of prepared glasses, i.e. Tg (glass transition temperature), Tx (onset of crystallization peak temperature), Tf (temperature of the inflection point of the crystallization peak) and Tp (maximum of crystallization peak temperature), were estimated from the DSC records. High-temperature XRD experiments in the temperature interval range 600–1100°C were also performed. The PL emission properties of prepared glasses and their polycrystalline analogues (glass crystallized at 1000°C for 10 h) were studied in the visible and near-infrared (NIR) spectral range. When excited at 300 nm, the glasses, as well as their polycrystalline analogues, exhibit broad emission in the visible spectral range from 350 to 650 nm centred at about 410–450 nm, corresponding to Bi3+ luminescence centres. The emission intensity of polycrystalline samples was found to be at least 30 times higher than the emission of their glass analogues. In addition, a weak emission band was observed around 775 nm under 300 nm excitation. This band was attributed to the presence of a minor amount of Bi2+ species in prepared samples. In the NIR spectral range, the broad band emission was observed in the spectral range of 1200–1600 nm with the maxima at 1350 nm. The chemistry of Bi and its oxidation state equilibrium in glasses and polycrystalline matrices is discussed in detail.

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Sr2(Mg1−Ga )Ge2O7+0.5: Melilite-type oxygen ionic conductor associated with fivefold coordinated germanium and gallium

Cited by 8 publications

References 23 publications

Sol—gel approach to low-temperature synthesis of single-phase metastable La2Ga3O7.5 melilite with enhanced grain-boundary oxide ionic conductivity via a kinetically favorable mechanism

Sol—gel approach to low-temperature synthesis of single-phase metastable La2Ga3O7.5 melilite with enhanced grain-boundary oxide ionic conductivity via a kinetically favorable mechanism

Development of Melilite‐Type Oxide Ion Conductors

Crystallization and visible–near-infrared luminescence of Bi-doped gehlenite glass

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