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Title: Synthesis and characterization of mixed phases in the Ca–Co–O system using the Pechini method

Highlights: ► We have prepared mixed Ca–Co–O phases using the Pechini method. ► Reaction times are reduced relative to conventional solid-state synthesis. ► Products have high surface area suitable for ceramic processing. ► Product composition is dictated by both kinetic and thermodynamic control. ► A revised phase diagram of the Ca–Co–O system is proposed. - Abstract: The synthesis of mixed phases in the Ca–Co–O system using the Pechini method was investigated. The phases CaCo{sub 2}O{sub 4}, Ca{sub 3}Co{sub 4}O{sub 9} and Ca{sub 3}Co{sub 2}O{sub 6}, which can be expressed in terms of the molar ratios of the binary oxides (CaO:Co{sub 2}O{sub 3}) as (1:1), (3:2) and (3:1) respectively, were obtained in pure form. Powder X-ray diffraction data showed they are comparable with materials obtained by conventional solid-state synthesis. The mild synthesis conditions of the Pechini method allowed the evolution of the Ca–Co–O phases to be studied as a function of temperature and heating time. Both variables have a strong influence on the composition of the products, indicating that both kinetic and thermodynamic factors play a role, with the former being of more importance at lower temperatures. The (1:1) phase, previously not identified in the phase diagram of the Ca–Co–O system,more » was obtained preferentially across the composition range below ca. 650 °C. The (3:2) phase was preferred until ca. 800 °C. At even higher temperatures, the (3:1) phase is obtained. The upper thermal stability limit of mixed phases in the Ca–Co–O system increases with the Ca:Co ratio. An updated phase diagram for the Ca–Co–O system is proposed.« less
Authors:
;  [1] ;  [2] ;  [1]
  1. College of DuPage, 425 Fawell Blvd, Glen Ellyn, IL 60137-6599 (United States)
  2. Department of Chemistry, Youngstown State University, 1 University Plaza, Youngstown, OH 44555-3663 (United States)
Publication Date:
OSTI Identifier:
22290455
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Research Bulletin; Journal Volume: 48; Journal Issue: 7; Other Information: Copyright (c) 2013 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CALCIUM OXIDES; CERAMICS; COBALT OXIDES; MAGNETIC MATERIALS; PHASE DIAGRAMS; SEMICONDUCTOR MATERIALS; SURFACE AREA; SYNTHESIS; TEMPERATURE DEPENDENCE; X-RAY DIFFRACTION