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Effect of YF3 on hot-pressed hydroxyapatite and monoclinic zirconia composites

Evis, Zafer
Doremus, Robert H.
Monoclinic zirconia and hydroxyapatite (HA) composites with or without 5 wt% YF3 were synthesized to investigate their mechanical properties and phase stability. HA decomposed to tri-calcium-phosphate and CaZrO3 in the 25 wt% ZrO2-75 wt% HA composite. However, thermal stability of the phases, densification, hardness and fracture toughness were improved when 5 wt% YF3 was added into the system. Five weight percent YF3 increased the transformation of monoclinic-ZrO2 into tetragonal/cubic-ZrO2 by incorporating the Y3+ ions present in YF3 when the hot pressing temperature was increased from 1100 to 1200 degrees C. Moreover, the stability of HA was also improved by incorporating the F- ions from YF3 in the place of OH- ions in HA. Substitution of OH- by F- ions was verified by the change in HA's hexagonal lattice parameters. A fracture toughness of 1.93 MPa root m was calculated for the same composite.