  Although infrared (IR) overall dust emission from clusters of galaxies has
been statistically detected using data from the Infrared Astronomical Satellite
(IRAS), it has not been possible to sample the spectral energy distribution
(SED) of this emission over its peak, and thus to break the degeneracy between
dust temperature and mass. By complementing the IRAS spectral coverage with
Planck satellite data from 100 to 857 GHz, we provide new constraints on the IR
spectrum of thermal dust emission in clusters of galaxies. We achieve this by
using a stacking approach for a sample of several hundred objects from the
Planck cluster sample; this procedure averages out fluctuations from the IR
sky, allowing us to reach a significant detection of the faint cluster
contribution. We also use the large frequency range probed by Planck, together
with component-separation techniques, to remove the contamination from both
cosmic microwave background anisotropies and the thermal Sunyaev-Zeldovich
effect (tSZ) signal, which dominate below 353 GHz. By excluding dominant
spurious signals or systematic effects, averaged detections are reported at
frequencies between 353 and 5000 GHz. We confirm the presence of dust in
clusters of galaxies at low and intermediate redshifts, yielding an SED with a
shape similar to that of the Milky Way. Planck's beam does not allow us to
investigate the detailed spatial distribution of this emission (e.g., whether
it comes from intergalactic dust or simply the dust content of the cluster
galaxies), but the radial distribution of the emission appears to follow that
of the stacked SZ signal, and thus the extent of the clusters. The recovered
SED allows us to constrain the dust mass responsible for the signal, as well as
its temperature. We additionally explore the evolution of the IR emission as a
function of cluster mass and redshift.
