  Based on differential thermal analysis (DTA) and X-ray powder diffraction
(XRD), a description of the system Nd$_2$O$_3$--Lu$_2$O$_3$--Sc$_2$O$_3$ was
obtained by thermodynamic assessment. Four fields of primary crystallization
could be identified; from melt compositions close to the
Lu$_2$O$_3$--Sc$_2$O$_3$ edge the rare-earth oxide C-phase crystallizes first,
which is stable down to room temperature. From Nd$_2$O$_3$ rich melts the
X-phase forms, which is stable only at high temperatures. An additional field,
where the alternative high-temperature phase H solidifies as primary product
touches the Nd$_2$O$_3$--Lu$_2$O$_3$ edge of the concentration triangle. From
melts close to the composition NdScO$_3$, the P-phase (perovskite) can be
crystallized and mixed crystals with second end member NdLuO$_3$ have been
grown from the melt. Crystals of this mixed perovskite were grown by the
micro-pulling-down and Czochralski methods.
