Hydrothermal Synthesis and Formation Mechanisms of Lanthanum Tin Pyrochlore Oxide

Joo Ho Moon, Masanobu Awano, Kunihiro Maeda

Research output: Contribution to journalArticle

33 Citations (Scopus)

Abstract

Well-defined La2Sn2O7 with a phase-pure pyrochlore structure was produced by hydrothermal synthesis at temperatures as low as 200°C. Production of phase-pure La2Sn2O7 requires a pH above 10, and higher pH accelerates the crystallization process. The synthesis produced spherical particles of average particle size ∼0.59 μm (±0.12) and surface area ∼14.1 m2/g. SEM and TEM observation for morphologic evolution and kinetic analysis during crystallization indicated that La2Sn2O7 formation probably proceeds via a two-step reaction. First a transient dissolution-precipitation occurs. Then the primary crystallites aggregate because of their colloidal instability, and heterocoagulation with the lanthanum hydrous oxide precursor particles also occurs. The sluggish reaction rate at the later stage of reaction is characterized by an in situ transformation, where the soluble tin species is diffused through the porous La2Sn2O7 aggregates to react with entrapped lanthanum precursors.

Original languageEnglish
Pages (from-to)2531-2536
Number of pages6
JournalJournal of the American Ceramic Society
Volume84
Issue number11
DOIs
Publication statusPublished - 2001 Jan 1

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Lanthanum oxides
pyrochlore
Hydrothermal synthesis
formation mechanism
Crystallization
Tin oxides
tin
crystallization
oxide
Lanthanum
Tin
Crystallites
reaction rate
Reaction rates
transmission electron microscopy
Dissolution
surface area
scanning electron microscopy
Particle size
dissolution

All Science Journal Classification (ASJC) codes

  • Ceramics and Composites
  • Materials Chemistry

Cite this

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abstract = "Well-defined La2Sn2O7 with a phase-pure pyrochlore structure was produced by hydrothermal synthesis at temperatures as low as 200°C. Production of phase-pure La2Sn2O7 requires a pH above 10, and higher pH accelerates the crystallization process. The synthesis produced spherical particles of average particle size ∼0.59 μm (±0.12) and surface area ∼14.1 m2/g. SEM and TEM observation for morphologic evolution and kinetic analysis during crystallization indicated that La2Sn2O7 formation probably proceeds via a two-step reaction. First a transient dissolution-precipitation occurs. Then the primary crystallites aggregate because of their colloidal instability, and heterocoagulation with the lanthanum hydrous oxide precursor particles also occurs. The sluggish reaction rate at the later stage of reaction is characterized by an in situ transformation, where the soluble tin species is diffused through the porous La2Sn2O7 aggregates to react with entrapped lanthanum precursors.",
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Hydrothermal Synthesis and Formation Mechanisms of Lanthanum Tin Pyrochlore Oxide. / Moon, Joo Ho; Awano, Masanobu; Maeda, Kunihiro.

In: Journal of the American Ceramic Society, Vol. 84, No. 11, 01.01.2001, p. 2531-2536.

Research output: Contribution to journalArticle

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AB - Well-defined La2Sn2O7 with a phase-pure pyrochlore structure was produced by hydrothermal synthesis at temperatures as low as 200°C. Production of phase-pure La2Sn2O7 requires a pH above 10, and higher pH accelerates the crystallization process. The synthesis produced spherical particles of average particle size ∼0.59 μm (±0.12) and surface area ∼14.1 m2/g. SEM and TEM observation for morphologic evolution and kinetic analysis during crystallization indicated that La2Sn2O7 formation probably proceeds via a two-step reaction. First a transient dissolution-precipitation occurs. Then the primary crystallites aggregate because of their colloidal instability, and heterocoagulation with the lanthanum hydrous oxide precursor particles also occurs. The sluggish reaction rate at the later stage of reaction is characterized by an in situ transformation, where the soluble tin species is diffused through the porous La2Sn2O7 aggregates to react with entrapped lanthanum precursors.

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