Low Temperature Synthesis of Porous NZP Ceramics
Abstract:Porous phase-pure NaZr2(PO4)3 monoliths were synthesized at 850°C from gels that precipitated as a consequence of mixing water-soluble precursors. The sintering temperature was limited to 850°C to permit densification in a range where NZP exhibits a low coefficient of thermal expansion. Attempts to maximize mechanical properties were made by both physical and chemical means. Particulate hydroxyapatite (HAp) was physically blended with the precipitated gels to template the crystallization of NZP. Copper nitrate was dissolved into solution as a sintering aid to stimulate liquid-phase sintering during firing. NZP made without these additives attained a specific surface area of 30 m2/g. The addition of HAp reduced the internal surface area to 5 m2/g. X-ray diffraction and scanning electron microscopy did not detect the presence of HAp in the fired samples, indicating it had been consumed during firing. Copper nitrate decomposed to CuO and its presence as a sintering aid resulted in enhanced densification and greater strengths. The presence of 5% CuO (as copper nitrate) together with 5% HAp resulted in a 40% volume shrinkage during firing. The tensile strength attained for this composition was 20 MPa as compared with that of approximately 8 MPa for the compositions fired without additives.
Document Type: Research Article
Affiliations: Department of Materials Science and Engineering, Penn State University, University Park, Pennsylvania 16802
Publication date: 2008-06-01