Single-crystal elasticity of Zn2TiO4-spinel up to 18 GPa

The single-crystal elastic constants of the spinel phase of Zn2TiO4 have been studied for the first-time using Brillouin scattering up to 18 GPa at room temperature in a diamond anvil cell. The three independent elastic constants of Zn2TiO4 spinel at ambient conditions were calculated: C-11 = 226(3), C-12 = 137(4) and C-44 = 88(2). The bulk modulus (K-S0) is 167(3) GPa, with pressure derivative K-s' = 5.3(2), and the shear modulus (G(0)) is 67(1) GPa, with pressure derivative G' = 0.06(5). On basis of previous studies, our results suggest a possibility of the general law of elastic constants with pressure derivative (C-ijs') for spinel structure minerals: C-11' approximate to C-12' and C-44' << C-11' (C-12'). In addition, Zn2TiO4 have the lowest velocities and Vs gradient compared with the spinel type minerals in Earth's mantle. Our results indicate the incorporation of Zn and Ti in the structure of ringwoodite may have a negative effect on the sound velocities and Vs gradient of Earth's mantle transition zone.