Influence of Zn and Mg Doping on the Sintering Behavior and Phase Transformation of Tricalcium Phosphate Based Ceramics

Abstract:

β-tricalcium phosphate based ceramics (β-TCP) are resorbable biomaterials used as bone substitutive materials. Several ions can substitute specific Ca positions in the crystalline structure of TCP, so that general Me-TCP can be obtained. Particularly, magnesium can increase the temperature of β-α-TCP transformation while zinc stimulates the bone formation. In this work, the influence of magnesium or zinc ions on the sintering behavior of Me-TCP was investigated. The powders were produced through wet chemical synthesis with a freeze drying process. The powders were calcined and subsequently uniaxially pressed into pellets. The pellets were sintered up to 1300°C/1h. The influence of Mg or Zn doping was investigated by dilatometric studies, thermal analysis and XRD. The microstructure was evaluated through SEM. The results suggest that Mg increased temperature of β-α-TCP phase transformation. The Me-doped TCP samples can be considered as promising biomaterials, having stimulatory effect of Zn or suitable densification due to Mg addition.

• Periodical: Materials Science Forum (Volume 805)
• Pages: 706-711
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.805.706
• Online since: September 2014
• Authors: Karen C. Kai*, Carlos A.V.A. Machado, Luis Antonio Genova, Juliana Marchi
• Keywords: Doping Ions, Phase Transformation, Sintering Behavior, Tricalcium Phosphate

References

[9] Fig. 1 shows the XRD patterns of Me-TCP powders after calcination at 800oC/1h. It can be observed that β-TCP phase (ICDD 090169) was identified in all powders. This temperature was, thus, suitable for the complete CDHA→β-TCP phase transformation. Fig. 1: XRD pattern of pure and doped Mg- or Zn-TCP powders after calcination at 800oC/1h. The morphology of the TCP powders calcinated at 800oC/1h was evaluated by HR-SEM (Fig. 2). It can be seen the influence of Mg or Zn doping on the distribution and size of the TCP particles. It can be seen that all powders are agglomerated. The particle size distribution in all samples is homogeneous and narrow. It seems that doped powders (Figs. 2b and 2c) shows a decrease in particle size. Moreover, Mg doping (Fig. 2c) seems to be more effective for this behavior. C B A Fig. 2: Scanning electron micrographs of TCP powders after calcination at 800oC/1h: a) TCP, b) Zn-TCP, c) Mg-TCP. Fig. 3 shows the differential thermal analysis results for pure and doped TCP with different ions. It can be seen the influence of Ca-Zn/Mg doping on the phase transformation of TCP based ceramics. At lower temperatures, it is observed endothermic processes related to absorbed and structural water losses, as (1) and (2) respectively indicated. The CDHA → b-TCP phase transformation is characterized by an exotermic-endotermic process (peak 3) related to the CDHA desydroxilation, and, consequently, b-TCP phase formation.

[8] The last endotermic peak (peak 4, enlarged shown in Fig 3b) is associated with the β-TCP→α-TCP phase transformation. It can be seen that the Zn-TCP showed lower temperature of this phase transformation as compared with pure or Mg-TCP. Marchi et al.

DOI: 10.1111/j.1744-7402.2009.02384.x

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