Crystal structure, thermal expansion and conductivity of anisotropic La1−xSrxGa1−2xMg2xO3−y (x=0.05, 0.1) single crystals

Vasylechko, L.; Vashook, V.; Savytskii, D.; Senyshyn, Anatoliy; Niewa, Rainer; Knapp, Michael; Ullmann, H.; Berkowski, M.; Matkovskii, A.; Bismayer, U.

doi:10.1016/s0022-4596(03)00016-1

Cited by 67 publications

(68 citation statements)

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“…The very few existing studies on LSGM, mostly with lower dopant concentration, dealt with crystal structure, thermal conductivity and ionic conductivity. 7,12 Detailed information on the electronic conductivity of LSGM single crystals is not available so far.Measurements on polycrystalline materials often suffer from difficulties to discriminate between effects induced by grains and grain boundaries. In principle, impedance spectroscopy allows separation of resistive grain and grain boundary contributions and often a brick layer model is used for data analysis.…”

mentioning

confidence: 99%

Electronic and Ionic Conductivity of La_0.95Sr_0.05Ga_0.95Mg_0.05O_3-δ(LSGM) Single Crystals

Rupp

Głowacki

Fleig

2016

J. Electrochem. Soc.

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The defect chemistry and charge transport properties of La 0.95 Sr 0.05 Ga 0.95 Mg 0.05 O 3-δ (LSGM) single crystals, grown by the Czochralski technique, were studied by impedance spectroscopy performed over a wide temperature range (180-800 • C) and oxygen partial pressures from 0.21 to 1013 mbar. Owing to ion blocking Pt thin film electrodes impedance data showed a Warburg type 45 • slope in the complex impedance plane. The spectra were analyzed by means of a generalized transmission line model which yielded the electronic and ionic conductivity, chemical and dielectric capacitance and the oxygen chemical diffusion coefficient. Activation energies for electronic (0.89 eV) and ionic charge transport (0.95 eV at low and 0.56 eV at high temperatures) were determined. Oxygen partial pressure dependent measurements revealed that the p-type conductivity is exactly proportional to p O 2 1/4 and that the ionic transference number approaches 1 for low oxygen partial pressures and low temperatures. Additional Hebb-Wagner type DC polarization experiments were carried out to determine the n-and p-type conductivities in a broad chemical potential range and to verify the results obtained by the AC impedance measurements. Strontium and magnesium doped lanthanum gallate (LSGM) has been widely investigated as potential electrolyte material in solid oxide fuel cells (SOFC) and thus as promising alternative to the fluorite type electrolytes yttria stabilized zirconia (YSZ) and gadolinium doped ceria (GDC). At lower temperatures (<700• C) the ionic conductivity of LSGM can exceed the conductivity of YSZ by more than a factor of 5 1-3 . Although the ionic conductivity below ca. 600• C is smaller compared to GDC, LSGM has the advantage of a broad electrolytic domain with negligible electronic conductivity under typical reducing and oxidizing conditions of SOFCs.4,5 However, electrochemical properties of LSGM have been investigated almost exclusively on polycrystalline samples, 1,6-11 in contrast to YSZ where many studies are also available on single crystals. This is largely because of the difficulty to synthesize larger single crystals of the preferred composition La 0.8 Sr 0.2 Ga 0.8 Mg 0.2 O 3-δ with sufficient quality. The very few existing studies on LSGM, mostly with lower dopant concentration, dealt with crystal structure, thermal conductivity and ionic conductivity. 7,12 Detailed information on the electronic conductivity of LSGM single crystals is not available so far.Measurements on polycrystalline materials often suffer from difficulties to discriminate between effects induced by grains and grain boundaries. In principle, impedance spectroscopy allows separation of resistive grain and grain boundary contributions and often a brick layer model is used for data analysis. [13][14][15] However, this approach only works at lower temperatures (due to the limited frequency range of impedance spectroscopy) and for the total conductivity, which is largely ionic in LSGM. A separation of resistive bulk and grain boundary contributi...

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confidence: 99%

Electronic and Ionic Conductivity of La_0.95Sr_0.05Ga_0.95Mg_0.05O_3-δ(LSGM) Single Crystals

Rupp

Głowacki

Fleig

2016

J. Electrochem. Soc.

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“…This crystal was grown from the stochiometric melt in argon/1% oxygen atmosphere with a pulling rate of 1.2-2.5 mm/h. Chemical analysis confirmed that the cation composition of the crystal is identical to the initial concentration of its components [25]. The oxygen content was calculated based on charge neutrality.…”

Section: Sample Preparationmentioning

confidence: 78%

“…Positions of reflections (up to 30 in total) were used to refine the orientation matrix and sample-to-detector distance. The orthorhombic cell with parameters a = 5.499 Å, b = 7.794 Å, c = 5.538 Å [25] were used for indexing the Laue diffraction patterns. To start indexing, the first six multiplets were selected at intersections of crystallographic zones.…”

Section: Measurements and Processing Datamentioning

confidence: 99%

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Identification of the Domain Walls Configuration in the Ferroelastic Nanosize Material La_0.95Sr_0.05Ga_0.9Mg_0.1O_3-x

et al. 2010

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This paper deals with the identification of multidomain configuration in ferroelastic phases of La 0.95 Sr 0.05 Ga 0.9 Mg 0.1 O 3−x using polychromatic synchrotron X-ray radiation (Laue method).A nondestructive approach for the determination of domain misorientations, orientation of domain walls and their configuration in the nanosize ferroelastic domain structure was developed. The proposed approach can be used to study the nanosize ferroelastic domain structure in small crystals of submillimeter sizes at different external fields, including temperature. The ferroelastic domain structure in the orthorhombic as well as in the rhombohedral phases of La 0.95 Sr 0.05 Ga 0.9 Mg 0.1 O 3−x crystals has been identified. The intersection of walls leads to the formation of a chevron-like pattern. The observed reversibility of domain patterns during temperature cycles is probably caused by the interaction of domain boundaries with point defects, most likely oxygen vacancies.

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“…The study of the LSGM05 crystal structure by the high resolution synchrotron powder diffraction [37] has demonstrated that the orthorhombic symmetry (Imma space group) is characteristic at room temperature. Heating the LSGM05 crystal up to 520-570 K involves phase transition, with the crystal point symmetry being reduced to the monoclinic one (I2/a space group).…”

Section: Possible Domain Configurations In Ferroelastic Phases Of Lsgmentioning

confidence: 99%

Theoretical Study of the Ferroelastic Domain Structure in La_0.95Sr_0.05Ga_0.9Mg_0.1O_3-x

et al. 2010

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Theoretical analysis of the ferroelastic domain structure of a La 0.95 Sr 0.05 Ga 0.9 Mg 0.1 O 2.925 crystal in three different crystallographic phases is presented. Parameters of these configurations are obtained using group theoretical approach, the method of spontaneous deformation as well as theoretical interpretation of twinning resulting from mechanical deformation (mechanical twinning theory). In the three phases of La 0.95 Sr 0.05 Ga 0.9 Mg 0.1 O 2.95 -trigonal, orthorhombic and monoclinic -the parameters of ferroelastic domain structures are determined; namely the quantity of orientation states, symmetry elements of connection between states, orientations and types of domain walls, tensors of spontaneous deformations of the perovskite-type cells for every orientation state, elements of twin shifts, which are needed for the reorientation of some orientation states to others. By using the found parameters of bidomain configurations a mechanism is proposed, which causes chevron-like domain configurations in compounds with martensitic phase transitions.

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Crystal structure, thermal expansion and conductivity of anisotropic La1−xSrxGa1−2xMg2xO3−y (x=0.05, 0.1) single crystals

Cited by 67 publications

References 22 publications

Electronic and Ionic Conductivity of La_0.95Sr_0.05Ga_0.95Mg_0.05O_3-δ(LSGM) Single Crystals

Electronic and Ionic Conductivity of La_0.95Sr_0.05Ga_0.95Mg_0.05O_3-δ(LSGM) Single Crystals

Identification of the Domain Walls Configuration in the Ferroelastic Nanosize Material La_0.95Sr_0.05Ga_0.9Mg_0.1O_3-x

Theoretical Study of the Ferroelastic Domain Structure in La_0.95Sr_0.05Ga_0.9Mg_0.1O_3-x

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Crystal structure, thermal expansion and conductivity of anisotropic La1−xSrxGa1−2xMg2xO3−y (x=0.05, 0.1) single crystals

Cited by 67 publications

References 22 publications

Electronic and Ionic Conductivity of La0.95Sr0.05Ga0.95Mg0.05O3-δ(LSGM) Single Crystals

Electronic and Ionic Conductivity of La0.95Sr0.05Ga0.95Mg0.05O3-δ(LSGM) Single Crystals

Identification of the Domain Walls Configuration in the Ferroelastic Nanosize Material La0.95Sr0.05Ga0.9Mg0.1O3-x

Theoretical Study of the Ferroelastic Domain Structure in La0.95Sr0.05Ga0.9Mg0.1O3-x

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Electronic and Ionic Conductivity of La_0.95Sr_0.05Ga_0.95Mg_0.05O_3-δ(LSGM) Single Crystals

Electronic and Ionic Conductivity of La_0.95Sr_0.05Ga_0.95Mg_0.05O_3-δ(LSGM) Single Crystals

Identification of the Domain Walls Configuration in the Ferroelastic Nanosize Material La_0.95Sr_0.05Ga_0.9Mg_0.1O_3-x

Theoretical Study of the Ferroelastic Domain Structure in La_0.95Sr_0.05Ga_0.9Mg_0.1O_3-x