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

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 °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√m was calculated for the same composite.