  The structural transformation of multiferroic EuTiO$_3$ has been intensively
investigated by synchrotron x-ray diffraction at pressures up to 50.3 GPa and
temperatures from 50 to 500 K. An antiferrodistortive phase transition from
cubic Pm-3m to tetragonal I4/mcm space group has been observed, identical to
the one that has been previously explored at ambient pressure and low
temperatures. Several compression/decompression cycles at different
temperatures have been carried out to accurately map the transition, and as a
result a P-T phase diagram for EuTiO$_3$ has been constructed. The observed
phase transition exhibits many similarities with isostructural SrTiO$_3$,
although the absence of magnetoelectric interactions in the latter accounts for
the different phase boundaries between the two materials.
