Synthesis of complex metal oxides using hydroxide, cyanide, and nitrate solid solution precursors

Vidyasagar, K.; Gopalakrishnan, J.; Rao, C. N. R.

doi:10.1016/0022-4596(85)90266-x

Cited by 87 publications

(32 citation statements)

References 19 publications

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“…Thermal decomposition of mixed cation (Mg,Ca,Mn)-siderites have been investigated under a wide variety of conditions, not only because of their geochemical importance, but also because they provide a convenient synthetic route to the preparation of complex metal oxides via the so-called 'solid-solution-precursor' method (Vidyasagar et al, 1984;Vidyasagar et al, 1985). The results of such studies are summarized in Table 6 and invariably demonstrate that thermal decomposition yields a mixed metal oxide phase as the product 17 .…”

Section: Prior Studiesmentioning

confidence: 99%

Origins of magnetite nanocrystals in Martian meteorite ALH84001

Thomas‐Keprta

Clemett

McKay

et al. 2009

Geochimica et Cosmochimica Acta

108

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The Martian meteorite ALH84001 preserves evidence of interaction with aqueous fluids while on Mars in the form of microscopic carbonate disks. These carbonate disks are believed to have precipitated 3.9 Ga ago at beginning of the Noachian epoch on Mars during which both the oldest extant Martian surfaces were formed, and perhaps the earliest global oceans. Intimately associated within and throughout these carbonate disks are nanocrystal magnetites (Fe 3 O 4 ) with unusual chemical and physical properties, whose origins have become the source of considerable debate. One group of hypotheses argues that these magnetites are the product of partial thermal decomposition of the host carbonate. Alternatively, the origins of magnetite and carbonate may be unrelated; that is, from the perspective of the carbonate the magnetite is allochthonous. For example, the magnetites might have already been present in the aqueous fluids from which the carbonates were believed to have been deposited. We have sought to resolve between these hypotheses through the detailed characterization of the compositional and structural relationships of the carbonate disks and associated magnetites with the orthopyroxene matrix in which they are embedded. Extensive use of focused ion beam milling techniques has been utilized for sample preparation. We then compared our observations with those from experimental thermal decomposition studies of sideritic carbonates under a range of plausible geological heating scenarios. We conclude that the vast majority of the nanocrystal magnetites present in the carbonate disks could not have formed by any of the currently proposed thermal decomposition scenarios. Instead, we find there is considerable evidence in support of an alternative allochthonous origin for the magnetite unrelated to any shock or thermal processing of the carbonates.

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Section: Prior Studiesmentioning

confidence: 99%

Origins of magnetite nanocrystals in Martian meteorite ALH84001

Thomas‐Keprta

Clemett

McKay

et al. 2009

Geochimica et Cosmochimica Acta

108

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“…A low-temperature preparative route using the citrate sol-gel method (Rosseinsky, Prassides & Day, 1989) often led to the presence of BaPbO3 as an impurity. High purity samples were prepared by an adaptation of the method of Vidyasagar, Gopalakrishnan & Rao (1985). Stoichiometric quantities of barium and lead nitrates are dissolved in the minimum quantity of distilled water.…”

Section: =mentioning

confidence: 99%

Time-of-flight powder neutron diffraction study of the structure of Ba2PbO4

Rosseinsky¹,

Prassides²

1991

Acta Crystallogr C

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Our results confirm the room-temperature structure determined earlier by X-ray work and show the lack of structural distortions down to 5 K. They also permit a very precise determination of the geometry of the PbO6 octahedra, showing that the tetragonal distortion had been overestimated before by at least a factor of 10. The implication of this result for recent band-structure calculations is stressed.

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“…Although the solid-state reaction is very simple, this process is not entirely satisfactory because of several serious drawbacks such as introduction of impurities during milling, high reaction temperature, limit of complete oxide reaction and chemical homogeneity, large particle sizes and low sintering ability [17,18]. Therefore, extensive investigations have been performed for preparing finer and more homogeneous powders at lower temperatures using various chemical processes.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, extensive investigations have been performed for preparing finer and more homogeneous powders at lower temperatures using various chemical processes. Vidyasagar et al [18] have obtained pure LaAlO 3 powders by calcining the precursor at 947 •C for 12 h in air via urea solution route. Pure LaAlO 3 powders have been synthesized at 860 •C using polyacrylamide by Douy and Odier [19].…”

Section: Introductionmentioning

confidence: 99%

“…Chemical coprecipitation route is a simple method for synthesizing nanopowders [25].The base precipitant most used in this method is NH 4 OH. Recently, Li et al [17]; Nair et al [26]; and Kuo et al [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] have used this method to synthesize pure LaAlO 3 using the mixed solution of NH 4 OH and calcined at 700, 800 and 1000 •C, respectively. However, the synthesis of lanthanum monoaluminate has been rarely reported using a mixture of sodium hydroxide such as base precipitant In the present study, nanocrystalline LaAlO 3 powders have been successfully synthesized using the mixed solution of NaOH in low temperature range of 500-1000 •C and pH 9.…”

Section: Introductionmentioning

confidence: 99%

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Synthesis and characterization of lanthanum monoaluminate by co-precipitation method

Djoudi

Omari

Madoui

2012

EPJ Web of Conferences

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Abstract.Our contribution has focused on the synthesis and characterization of lanthanum monoaluminate LaAlO3 by the method of co-precipitation. The powder was successfully synthesized using NaOH, La (NO 3 ) 3 .6H 2 O and Al (NO 3 ) 3 .9H 2 O as raw materials by this method and calcined at different temperatures. It was characterized by several techniques: Fourier transform infrared spectroscopy (FT-IR), thermogravimetric and differential thermal analysis (TGA/DTA), X-ray diffraction (XRD) and laser diffusion. All the results for physico-chemicals characterizations show that the crystallization temperature of the LaAlO 3 precursor gels precipitated is estimated as 790 °C by TG/DTA. The XRD pattern of the LaAlO 3 precursor gels calcined at 700 •C for 6 h has a perovskite structure of rhombohedral hexagonal phase formed and the presence of crystalline impurities is not found. The crystallite size of LaAlO 3 slightly increases from 31to 44.5 nm with calcination temperature increasing from 700to1000 °C for 6 h.

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Synthesis of complex metal oxides using hydroxide, cyanide, and nitrate solid solution precursors

Cited by 87 publications

References 19 publications

Origins of magnetite nanocrystals in Martian meteorite ALH84001

Origins of magnetite nanocrystals in Martian meteorite ALH84001

Time-of-flight powder neutron diffraction study of the structure of Ba2PbO4

Synthesis and characterization of lanthanum monoaluminate by co-precipitation method

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