Growth and characterization of large YBa2Cu3O7−x single crystals

Keester, Kenneth L.; Housley, R. M.; Marshall, David B.

doi:10.1016/0022-0248(88)90241-2

Cited by 31 publications

(7 citation statements)

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“…According to our data, however, the a factors of Y123 under the measured oxygen partial pressures are still very large compared to those of metals. The grown single crystals of Y123 have shown a faceted growth nature, [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] which is indicative of a large a factor.…”

Section: Resultsmentioning

confidence: 98%

Oxygen partial pressure dependence of the yttrium solubility in Y–Ba–Cu–O solution

1996

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The ytrrium solubility in Ba-Cu-O solvent with a Ba to Cu ratio of 3 to 5 was investigated under different oxygen partial pressure [P(O 2 ) 2, 21, 100%]. A small amount of the solution was taken out by dipping thermally equilibrated MgO single crystals, and compositions of these specimens were analyzed by inductively coupled plasma atomic emission spectrometry (ICP-AES). The measurements were performed for the samples prepared in the temperature range from approximately 950 ± C up to 1100 ± C. The peritectic temperature of YBa 2 Cu 3 O 72x (Y123) decreased with decreasing oxygen partial pressure. On the other hand, the Y123 liquidus lines do not show remarkable oxygen partial pressure dependency. Accordingly, the yttrium solubility at the peritectic temperature of Y123 under P(O 2 ) 100% was larger than those for the other conditions [P(O 2 ) 2% and 21%]. Assuming a regular solution, expressions for the solubility and the enthalpy of dissolution of Y123 and Y 2 BaCuO 5 (Y211) were derived from classical thermodynamic calculations and found to be 289 kJ͞mol at P͑O 2 ͒ 0.02, 239 kJ͞mol at P͑O 2 ͒ 0.21 atm, 206 kJ͞mol at P͑O 2 ͒ 1 atm for Y123, and 105 kJ͞mol at P͑O 2 ͒ 0.02 atm, 88.0 kJ͞mol at P͑O 2 ͒ 0.21 atm, and 88.4 kJ͞mol at P͑O 2 ͒ 1 atm for Y211. Furthermore, the Jackson a factor of Y123 was estimated to be about 20, confirming a faceted growth nature of this crystal.

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Section: Resultsmentioning

confidence: 98%

Oxygen partial pressure dependence of the yttrium solubility in Y–Ba–Cu–O solution

1996

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“…For example, Fe Lβ/Lα appears to decrease with increasing oxidation state for iron oxides, but is much smaller in Fe metal than any of the oxides (e.g., ref ). On the other hand, Cu Lβ/Lα is greater in the oxides than in the pure metal and appears to increase with increasing oxidation state; a comparison of Cu Lβ/Lα in YBa 2 Cu 3 O 6+ x with that in Cu, Cu 2 O, and CuO appears to be consistent with Cu being in the +3 oxidation state (e.g., refs −54; also see Figure , below).…”

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confidence: 81%

“…(3) systematic variations in the Lβ/LR intensity ratios with oxidation state and complicated variations with the bonding environment for Ti, 20 Mn, 42,43 Fe, 20,[35][36][37]42,[44][45][46][47] and Cu. 2, [48][49][50][51][52] Interpretation of these spectral features is complicated by (1) the large amount of self-absorption of these X-rays, (2) the close proximity of absorption and X-ray lines that cause variation in the spectral shape as a function of the electron beam energy (e.g., refs [53][54][55][56], and (3) possible reduction reactions under electron bombardment that result in spectral shape changes with increasing beam current (e.g., refs 55 and 56).…”

mentioning

confidence: 99%

“…Most attempts to determine chemical valence states of the first-row transition elements using X-ray emission spectroscopy with electron microbeam instruments have concentrated on measurement of the L II −L III (Lβ and Lα) spectra. Reports have been made of the following: (1) wavelength shifts of Cu and Fe − with oxidation state; (2) variations in the peak widths and shapes of the L II −L III (particularly Lβ) spectra of Fe, ,, Mn to Ga, and Ti to Zn , with oxidation state and bonding environment; and (3) systematic variations in the Lβ/Lα intensity ratios with oxidation state and complicated variations with the bonding environment for Ti, Mn, , Fe, ,− ,,− and Cu. ,− Interpretation of these spectral features is complicated by (1) the large amount of self-absorption of these X-rays, (2) the close proximity of absorption and X-ray lines that cause variation in the spectral shape as a function of the electron beam energy (e.g., refs −56), and (3) possible reduction reactions under electron bombardment that result in spectral shape changes with increasing beam current (e.g., refs and ).…”

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confidence: 99%

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Determination of Chemical Valence State by X-ray Emission Analysis Using Electron Beam Instruments: Pitfalls and Promises

Armstrong

1999

Anal. Chem.

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The use of X-ray emission spectroscopy to determine the valence states of first-row transition elements is evaluated using measurements of X-ray wavelength shifts, line shapes, and relative X-ray line intensities (Lβ/Lα and Kβ/Kα). X-ray wavelength (or energy) centroids and line shapes are shown to vary not only with oxidation state but also with chemical bonding for the same oxidation state. In many of the cases studied, the ratio of Kβ to Kα is shown to vary depending upon the differential absorption at a similar level to what is cited in the literature as due to the valence state. Similarly, in a number of cases studied, the ratio of Lβ to Lα is shown to vary by differences in self-absorption (and at low electron beam energies, differences in overvoltage) by levels comparable to what is ascribed in the literature as due to valence state. Differences were found among compounds with different oxidation states that exceeded the magnitude predicted by absorption or overvoltage effects; however, no systematic variations were found that were dependent only on the valence state of the element (as opposed to which other elements it was bonded). The results show that oxidation state cannot be simply and unambiguously determined by X-ray emission spectroscopy at the resolution obtainable with conventional wavelength-dispersive detectors on electron microscopes or microprobes. Of the various techniques employed in X-ray emission spectroscopy, the most promising for oxidation-state determination appears to be measurement of the wavelength shift and/or satellite line shape variation, but then only when comparing compounds in which the cation has the same bonding environment. It is critically important to correct for self-absorption effects when attempting to relate variations in Lβ/Lα to differences in oxidation state or bonding environment, regardless of the electron beam energy used in analysis. Specifically, Lβ/Lα measurements cannot be used to determine the oxidation state of Cu in high-temperature superconductors.

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“…Numerous preparation routes for the growth of single crystals have been reported (Balestrino et al 1987;Das et al 1987;Hayashi et al 1987;Hidaka et al 1987;Kaiser et al 1987;Scheel and Licci 1987;Schneemeyer et al 1987; Takei et al 1987;Takekawa and Iyi 1987;Keester et al 1988;Taylor et al 1988;Bosi et al 1989;Sun et al 1989;Taylor 1990;Watanabe 1990) since the discovery of the high temperature superconducting material . Since this compound melts incongruently above 1000°C, depending on the oxygen partial pressure, it is not possible to grow crystals from the stoichiometric melt, and a flux growth method appears to offer the most successful route at the present time.…”

Section: Introductionmentioning

confidence: 99%

Growth and Properties of Large Single Crystals of YBa2Cu3O7-d from BaCuO2/CuO Flux

Hunter¹,

Town²,

Matthews³

et al. 1991

Aust. J. Phys.

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Large single crystals of YBa2Cu307-o have been grown using a BaCu02/CUO flux whose composition lies close to the eutectic in the Y-Ba-Cu-o phase diagram. While the largest crystals produced were '" 20x20xO· 7 mm 3 , the average size of the remaining crystals was approximately 10x10xO· 5 mm 3 . These crystals, both as-grown and oxygen annealed, have been characterised using susceptibility measurements, optical and scanning microscopy and X-ray and neutron diffraction techniques.

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Growth and characterization of large YBa2Cu3O7−x single crystals

Cited by 31 publications

References 10 publications

Oxygen partial pressure dependence of the yttrium solubility in Y–Ba–Cu–O solution

Oxygen partial pressure dependence of the yttrium solubility in Y–Ba–Cu–O solution

Determination of Chemical Valence State by X-ray Emission Analysis Using Electron Beam Instruments: Pitfalls and Promises

Growth and Properties of Large Single Crystals of YBa2Cu3O7-d from BaCuO2/CuO Flux

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