"Oxidation Of Tetragonal PbO In Air" by Charles A. Sorrell
 

Abstract

Isothermal oxidation of tetragonal PbO in air produced multiphase assemblages with apparent equilibrium compositions which varied linearly with temperature from PbO1.548 at 286°C to PbO1.333 at 351°C. Oxidation at each temperature was relatively rapid to PbO1.40 and very slow from PbO1.40 to apparent equilibrium values. Pseudocubic PbO1+x, with compositions between PbO1.41 and PbO1.57, was indexed on a cubic unit cell at the lower O/Pb ratios and on a tetragonal unit cell at the higher ratios. Linear changes in lattice parameters and deviation from cubic symmetry accompanied reversible oxidation and reduction of the phase. Pseudocubic PbO1+x was reduced irreversibly to Pb3O4 below the composition PbO1.41. Hexagonal PbO1+x, with compositions between PbO1.333 and PbO1.41, developed to a maximum of 60% at intermediate temperatures. The hexagonal phase oxidized irreversibly to pseudocubic PbO1+x at lower temperatures and reduced irreversibly to Pb3O4 at higher temperatures. The extent of oxidation at a given temperature was greater in PbO with a mean diameter of 0.52 μm than in PbO with a mean diameter of 2.89 μm, indicating a metastable assemblage. Linear variation of oxidation limits with temperature across the composition boundary between the PbO1+x phases suggests that the free energies are equal at PbO1.41, with the lower limit of pseudocubic PbO1+x determined by tolerance of the structure for oxygen vacancies. Copyright © 1973, Wiley Blackwell. All rights reserved

Department(s)

Materials Science and Engineering

Publication Status

Full Access

International Standard Serial Number (ISSN)

1551-2916; 0002-7820

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2023 Wiley, All rights reserved.

Publication Date

01 Jan 1973

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