Synthesis and sintering of hydroxyapatite–zirconia composites

Fabrication and characterization of sol–gel derived hydroxyapatite/zirconia composite nanopowders with various yttria contents

“…Therefore, the resulting powder is less reactive with CaO than the pure monoclinic ZrO 2 is. It has been reported that, the reason for this lower reactivity is that the diffusion of CaO in ZrO 2 containing some Y 2 O 3 is slower than in ZrO 2 without it [29,31]. Thus, the effect of Y 2 O 3 is apparently one of reducing the diffusion coefficient of CaO in ZrO 2 [31].…”

“…Hence, the optimization of the calcination temperature is of great importance. Addition of a ZrO 2 phase such as 0YSZ to the HA matrix decreases the decomposition temperature of HA, so that HA starts to decompose into a mixture of TCP and CaO and that HA will react with the monoclinic (m)-ZrO 2 phase resulting in the formation of calcia-stabilized ZrO 2 according to the following reaction [29]: This behavior is different from that of pure HA, so that ZrO 2 act as a catalyst for the decomposition of HA [29]. Some CaO will subsequently dissolve into zirconia to form a solid solution followed by a phase change from the tetragonal phase to the cubic phase with the formation of calcia-stabilized zirconia, as shown in the CaO-ZrO 2 [30] phase diagram.…”

“…The other CaO will react with ZrO 2 to form calcium zirconate (CaZrO 3 ). Meanwhile, these reactions cause HA to become destabilized and decompose into more b-TCP phases [11,29]. On the other hand, as more CaO is available from HA decomposition, CaZrO 3 forms as in the following reaction.…”

Effect of ZrO2, TiO2, and Al2O3 Additions on Process and Kinetics of Bonelike Apatite Formation on Sintered Natural Hydroxyapatite Surfaces

“…[11][12][13][14][15][16] Rapacz-Kmita et al 13 have found that a coarse or fine or needle grained zirconia get better the mechanical properties of HA sintered at different temperatures (from 1100°C to 1300°C). [4][5][6][7] The addition of ZrO 2 decreases the decomposition temperature of HA into TCP (a-or b-TCP) from~1300-1400°C down tõ 1000-1150°C. [16][17][18] Fidancevska et al have shown that composite with 15% TiO 2 content improves mechanical properties.…”

Tailoring the Microstructure of Sol–Gel Derived Hydroxyapatite/Zirconia Nanocrystalline Composites

“…However, it has been reported that the addition of ZrO 2 causes an increase in the content of tricalcium phosphate (β-TCP, Ca 3 (PO 4 ) 2 ) [11], which seriously deteriorates the mechanical properties and chemical stability of these composites. In addition, calcium can be released from HA and interact with zirconium, resulting in the formation of cubic zirconia or calcium zirconate, which inhibits the toughening transformation mechanism [4,12-15]. …”