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Oxygen Vacancies in Pure Tetragonal Zirconia Powders: Dependence on the Presence of Chlorine during Processing
Author(s) -
Karapetrova Evguenia,
Platzer Roland,
Gardner John A.,
Torne Erwin,
Sommers James A.,
Evenson William E.
Publication year - 2001
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.2001.tb00609.x
Subject(s) - tetragonal crystal system , materials science , analytical chemistry (journal) , grain size , oxygen , chlorine , annealing (glass) , impurity , vacancy defect , phase (matter) , mineralogy , chemistry , crystallography , metallurgy , organic chemistry , chromatography
We have used several experimental methods to study how a large extrinsic oxygen vacancy density in pure tetragonal ZrO 2 powders depends on details of how those powders are made. Samples were made from oxychloride and nitrate precursor solutions. We used perturbed angular correlation spectroscopy to determine in situ phase structure and the density of oxygen vacancies at 1200°C, XRD and SEM to determine the grain size and morphology of samples annealed at temperatures ranging from 200°–1200°C, and neutron activation analysis (NAA) to investigate purity of samples. NAA results showed that samples contain cation impurities at levels <<100 ppm. The XRD and SEM measurements showed that grains were nanometer‐size, had a broad distribution, and grew from ∼10 nm at 200°C to ∼1 μm at 1200°C. The most striking process dependence is on presence of chlorine during processing. The grain size and phase above 600°C, and both the morphology and the density of oxygen vacancies at 1200°C were strongly affected by presence of chlorine‐containing vapor during annealing. Samples processed in a chlorine‐free atmosphere had large well‐sintered grains and large (>500 ppm) oxygen vacancy concentrations at 1200°C, whereas samples processed in flowing H 2 O/HCl vapor had smaller grains, porous morphology, and small (<100 ppm) vacancy density. All samples were loose powders consisting of single grain particles at <1000°C and multiple‐grain particles at 1200°C.