We present results from in situ x-ray diffraction studies of
hydrogenated icosahedral Ti-Zr-Ni quasicrystals carried out under
high pressure. The icosahedral Ti53Zr27Ni20 phase
and hydrogenated icosahedral Ti45Zr38Ni17 samples
that contain 0.32 and 1.45 hydrogen atoms for each metal atom were
studied. The icosahedral quasicrystal structure is retained up to
the highest pressures investigated. The six-dimensional lattice
parameter was obtained as a function of pressure for the different
samples. The zero-pressure bulk modulus and its pressure derivative
were determined by fitting a Murnaghan-type equation of state to the
relative volume change V/V0. The zero-pressure bulk modulus is
respectively obtained as B0 = 130±10, 105±10, and 110±20 GPa for H/M equal to 0, 0.32, and 1.45 using a constant value
for the first derivative B'0: 5.5±1. It seems, therefore,
that the icosahedral Ti-Zr-Ni phase may be more compressible after
hydrogenation, but there is no clear difference for different H/M
contents. These results are tentatively related to the local
structure of these materials.