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Silicon‐substituted hydroxyapatite ceramics (Si‐HAp): densification and grain growth through the prism of sintering theories
Author(s) -
Putlayev V.,
Veresov A.,
Pulkin M.,
Soin A.,
Kuznetsov V.
Publication year - 2006
Publication title -
materialwissenschaft und werkstofftechnik
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.285
H-Index - 38
eISSN - 1521-4052
pISSN - 0933-5137
DOI - 10.1002/mawe.200600007
Subject(s) - sintering , materials science , grain growth , doping , grain boundary , chemical engineering , ceramic , mineralogy , silicon , solubility , grain boundary diffusion coefficient , grain size , microstructure , nanotechnology , metallurgy , chemistry , optoelectronics , engineering
Ceramics based on calcium phosphates is known to be a prospective material for biomedical applications. Noticeable attention is paid to hydroxyapatite Ca 10 (PO 4 ) 6 (OH) 2 (HAp) due to its affinity to a bone mineral. It was recognized recently that Si‐doped HAp is a highly promising material in sense of bioactivity improvement. In the frame of distinct research activity structured around this subject, some special problems are to be solved: (1) solubility of Si in the bulk of HAp lattice (and its limit) vs. segregation of Si to free surfaces and grain boundaries, (2) rationalization of Si effect on sintering of HAp ceramics, (3) charge compensation over aliovalent doping of HAp with Si and its interplay with thermal stability of HAp phase. The work was focused on a fabrication of Si‐HAp with Ca 10 (Po 4 ) 6‐x (SiO 4 ) x (OH) 2‐x (x=0..1) nominal composition and evaluation the effect of Si on sintering of HAp ceramics. The limit of Si solubility in HAp lattice was estimated to be not higher than x=0.1 in the formula above (at 1000 °C, according to XRD and SEM/EDX). The essence of the silicon influence consists in significant suppression of grain growth during the initial stage of sintering. Silicon doping reduces grain boundary mobility (increasing activation energy of lattice diffusion) along with the increase of pore mobility (in fact, increasing grain boundary diffusion). We believe that the effect of Si on sintering behaviour can be treated in terms of its segregation to grain boundaries, the phenomenon arising from a lattice instability of Si‐HAp due to the charge compensation in the course of aliovalent doping.