Synthesis and characterization of Ti-doped ZrSiO₄ at ambient and high-pressure conditions

We have successfully synthesized for the first time a Ti-doped ZrSiO₄ powder (stoichiometry Zr_0.95Ti_0.05SiO₄) via a sol–gel route. The structural and vibrational properties have been characterized by X-ray diffraction, electron microscopy and Raman spectroscopy. Zr_0.95Ti_0.05SiO₄ has a tetragonal zircon-type structure with a = 6.5981(2) Å and c = 5.9810(2) Å. Eight of its Raman-active modes have been measured and assigned. We also performed high-pressure synchrotron X-ray diffraction experiments. The structural behavior was studied up to 31 GPa. At this pressure, we found evidence of the onset of a phase transition, coexisting the low-pressure polymorphs (zircon) with the typical high-pressure polymorph of ZrSiO₄ (reidite-type). From the analysis of unit-cell volume versus pressure using a Birch–Murnaghan equation of state, in the quasi-hydrostatic pressure regime (P < 10.5 GPa), we have determined a bulk modulus of 297 GPa. This magnitude represents an enhancement of a 30% in the value of this parameter if compared with un-doped zircon-type ZrSiO₄ (bulk modulus < 227 GPa). The low compressibility of Zr_0.95Ti_0.05SiO₄ converts this compound in a very good candidate for many technological applications. The effect of pressure on the linear compressibility of the lattice parameters is also analyzed.