Thermal behavior of gamma manganese dioxide: 2. Evolution of crystal defects related to structural water

Journal Article · Fri Oct 01 00:00:00 EDT 1993 · Materials Research Bulletin; (United States)

DOI:https://doi.org/10.1016/0025-5408(93)90148-7· OSTI ID:5938602

Petit, F; Lenglet, M; Arsene, J ^[1]

---

1. Univ. de ROUEN, Mont Saint Aignan (France). Lab. de Physicochimie des Materiaux

Electrochemically active manganese dioxides ([gamma]-MnO[sub 2]) contain physical and chemical crystal defects, related to structural water, which plays an important part in the mechanisms of proton insertion and migration in charge/discharge cycle. The loss of the structural water of two industrial samples of [gamma]-MnO[sub 2] (EMD and CMD) during static and dynamic thermal treatments in oxidizing atmosphere is studied using several experimental methods, in order to verify Ruetschi's model. The correlation of FTIR spectra, realized in-situ in temperature, with photoluminescence spectra enables the authors to associate hydroxyl groups with crystal point defects like Mn[sup 4+] vacancies. The residual presence of OH groups and Mn[sup 4+] vacancies at 400 C reveals that MnO[sub 2] is not stoichiometric at this temperature. This conclusion is corroborated by chemical measurements of manganese oxidation degrees of annealed samples, by thermogravimetric analysis and by the analysis of gas evolved during heat-treatment. Such results partially contradict Ruetschi's general formula of [gamma]-MnO[sub 2] and its overall waterloss process.

• OSTI ID: 5938602
• Journal Information: Materials Research Bulletin; (United States), Vol. 28:10; ISSN 0025-5408
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
MANGANESE OXIDES
CRYSTAL STRUCTURE
DEFECTS
TEMPERATURE DEPENDENCE
THERMAL GRAVIMETRIC ANALYSIS
WATER
CHALCOGENIDES
CHEMICAL ANALYSIS
GRAVIMETRIC ANALYSIS
HYDROGEN COMPOUNDS
MANGANESE COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
QUANTITATIVE CHEMICAL ANALYSIS
THERMAL ANALYSIS
TRANSITION ELEMENT COMPOUNDS
360202* - Ceramics
Cermets
& Refractories- Structure & Phase Studies