We report measurements of the neutron diffuse scattering in a single crystal of the
relaxor ferroelectric material 95.5%Pb(Zn1/3Nb2/3)O3-4.5%PbTiO3 (PZN-4.5%PT). We show
that the diffuse scattering at high temperatures has a quasielastic component with
energy width \(\agt\) 0.1 meV. On cooling the total diffuse scattering intensity increases,
but the intensity and the energy width of the quasielastic component gradually diminish.
At 50 K the diffuse scattering is completely static (i.e.the energy width lies within
the limits of our instrumental resolution). This suggests that the dynamics of the
short-range correlated atomic displacements associated with the diffuse scattering
freeze at low temperature. We find that this depends on the wave vector q as the quasielastic
diffuse scattering intensities associated with <001> (T1-type) and <110> (T2-type)
atomic displacements vary differently with temperature and electric field.