  We demonstrate that recent advances in nanoscale thermal transport and
temperature manipulation can be brought to bear on the problem of tailoring
thermal radiation from compact emitters. We show that wavelength-scale
composite bodies involving complicated arrangements of phase-change
chalcogenide (GST) glasses and metals or semiconductors can exhibit large
emissivities and partial directivities at mid-infrared wavelengths, a
consequence of temperature localization within the GST. We consider multiple
object topologies, including spherical, cylindrical, and mushroom-like
composites, and show that partial directivity follows from a complicated
interplay between particle shape, material dispersion, and temperature
localization. Our calculations exploit a recently developed fluctuating-volume
current formulation of electromagnetic fluctuations that rigorously captures
radiation phenomena in structures with both temperature and dielectric
inhomogeneities.
