Equation of state of a synthetic ulvöspinel, (Fe1.94Ti0.03)Ti1.00O4.00, at ambient temperature

Using a diamond-anvil cell and synchrotron X-ray diffraction, the compressional behavior of a synthetic ulvospinel (Fe1.94Ti0.03)Ti1.00O4.00 has been investigated up to about 7.05 GPa at 300 K. The pressure–volume data fitted to the second-order Birch–Murnaghan equation of state yield an isothermal bulk modulus (K T ) of 147(4) GPa (K′ T fixed as 4). This value is slightly larger than that previously determined by an ultrasonic pulse echo method (121(2) GPa; Syono et al., J Phys Soc Jpn 31:471–476, 1971), but substantially smaller than that recently determined by a synchrotron X-ray diffraction technique (251(3) GPa; Yamanaka et al., Phys Rev B 80:134120, 2009; Am Mineral 98:736–744, 2013). Combined with the K T of magnetite (Fe3O4; ~182(3) GPa), our finding suggests that the bulk modulus of the solid solutions Fe3−x Ti x O4 (0 ≤ x ≤ 1) along the join magnetite–ulvospinel decreases by ~20 %.