Synthesis, characterization, mechanical and magnetic characteristics of Gd 3+ /PO 4 3 - substituted zircon for application in hard tissue replacements.

The study reports on the use of sol-gel technique to yield zircon type [Zr (1-0.1-x) GdxTi 0.1 ] [(SiO 4 ) 1-x (PO 4 ) x ] solid solution. Titanium has been used as a mineralizer to trigger zircon formation while equimolar concentrations of Gd 3+ and PO 4 3- were added to determine their accommodation limits in the zircon structure. The crystallization of t-ZrO 2 as a dominant phase alongside the crystallization of m-ZrO 2 and zircon were detected at 1200°C while their further annealing revealed the formation of zircon as a major phase at 1300°C. Heat treatment at 1400°C revealed the formation of zircon-type solid solution [Zr (1-0.1-x) Gd x Ti 0.1 ][(SiO 4 ) 1-x (PO 4 ) x ] comprising the accommodation of 10 mol.% of Gd 3+ /PO 4 3- at the zircon lattice. Beyond 10 mol.% of Gd 3+ /PO 4 3- , the crystallization of GdPO 4 as a secondary phase is noticed. Structural analysis revealed the expansion of zircon lattice due to the simultaneous occupancy of Gd 3+ /PO 4 3- for the corresponding Zr 4+ /SiO 4 4- sites. The mechanical strength of single-phase zircon solid solution was higher in comparison to that of multiphase materials, namely in the presence of GdPO 4 formed as a secondary phase in samples with added equimolar Gd 3+ /PO 4 3- contents beyond 10 mol.%. Nevertheless, the paramagnetic behavior of the samples demonstrated a steady surge as a function of enhanced Gd 3+ content.