Nandha Kumar Ponnusamy, Ferreira José Maria da Fonte, Kannan Sanjeevi
Centre for Nanoscience and Technology, Pondicherry University , Puducherry 605 014, India.
Department of Materials and Ceramics Engineering, University of Aveiro, CICECO , Aveiro 3810 193, Portugal.
Inorg Chem. 2017 Feb 6;56(3):1289-1299. doi: 10.1021/acs.inorgchem.6b02445. Epub 2017 Jan 13.
Composites with varied proportions of β-Ca(PO) and ZnO were obtained through an in situ aqueous precipitation method under slightly basic (pH ≈ 8) conditions. The formation of β-Ca(PO) phase starts at an early heat-treatment stage (∼800 °C) and incorporates Zn ions at both Ca(4) and Ca(5) sites of the lattice up to its occupancy saturation limit. The incorporation of Zn in the β-Ca(PO) lattice enhances its thermal stability delaying the allotropic β-Ca(PO)→α-Ca(PO) phase transformation. The excess zinc beyond the occupancy saturation limit precipitates as Zn(OH) and undergoes dehydroxylation to form ZnO at elevated temperatures. The presence of ZnO in the β-Ca(PO) 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.
通过原位水沉淀法在弱碱性（pH≈8）条件下获得了具有不同比例β-Ca(PO)和ZnO的复合材料。β-Ca(PO)相的形成始于早期热处理阶段（约800°C），并在晶格的Ca(4)和Ca(5)位点掺入锌离子，直至其占据饱和极限。锌掺入β-Ca(PO)晶格中增强了其热稳定性，延迟了同素异形的β-Ca(PO)→α-Ca(PO)相变。超过占据饱和极限的过量锌以Zn(OH)形式沉淀，并在高温下发生脱羟基作用形成ZnO。β-Ca(PO)基体中ZnO的存在产生了更致密的微观结构，从而改善了烧结复合材料的机械性能，直至达到最佳ZnO浓度，超过该浓度则往往会产生相反的效果。
