Formation Mechanisms in β‑Ca3(PO4)2–ZnO Composites: Structural Repercussions of Composition and Heat Treatments

Composites with varied proportions of β-Ca3(PO4)2 and ZnO were obtained through an in situ aqueous precipitation method under slightly basic (pH ≈ 8) conditions. The formation of β-Ca3(PO4)2 phase starts at an early heat-treatment stage (∼800 °C) and incorporates Zn2+ ions at both Ca2+(4) and Ca2+(5...

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Bibliographic Details
Published in:Inorganic chemistry 2017-02, Vol.56 (3), p.1289-1299
Main Authors: Nandha Kumar, Ponnusamy, Ferreira, José Maria da Fonte, Kannan, Sanjeevi
Format: Article
Language:English
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Summary:Composites with varied proportions of β-Ca3(PO4)2 and ZnO were obtained through an in situ aqueous precipitation method under slightly basic (pH ≈ 8) conditions. The formation of β-Ca3(PO4)2 phase starts at an early heat-treatment stage (∼800 °C) and incorporates Zn2+ ions at both Ca2+(4) and Ca2+(5) sites of the lattice up to its occupancy saturation limit. The incorporation of Zn2+ in the β-Ca3(PO4)2 lattice enhances its thermal stability delaying the allotropic β-Ca3(PO4)2→α-Ca3(PO4)2 phase transformation. The excess zinc beyond the occupancy saturation limit precipitates as Zn­(OH)2 and undergoes dehydroxylation to form ZnO at elevated temperatures. The presence of ZnO in the β-Ca3(PO4)2 matrix yields denser microstructures and thus improves the mechanical features of sintered composites up to an optimal ZnO concentration beyond which it tends to exert an opposite effect.
ISSN:0020-1669
1520-510X
DOI:10.1021/acs.inorgchem.6b02445