  The pseudo-cubic lattice parameters of rare-earth (RE) scandate, REScO3,
single crystals grown by the Czochralski technique with RE=Dy to Pr lie between
about 3.95 and 4.02 Angstrom. These crystals are the only available perovskite
substrates in this lattice constant range that can withstand virtually any thin
film growth conditions. Two members of this series, PmScO3 and EuScO3, are,
however, not suitable for substrate applications. Because the pseudo-cubic
lattice parameters between neighbouring REScO3 compounds decrease with rising
atomic number of the RE in about 0.01 Angstrom steps, the unsuitability of
PmScO3 (radioactivity) and EuScO3 (incompatibility with Si) causes an
interruption in this lattice spacing sequence. To replace them, solid solutions
of their adjacent rare-earth scandates, i.e., (Nd0.5Sm0.5)ScO3 and
(Sm0.5Gd0.5)ScO3, were grown by the Czochralski method. Their average
pseudo-cubic lattice parameters of 3.9979 Angstrom and 3.9784 Angstrom are very
close to those of PmScO3 and EuScO3, respectively, and they show very low
segregation. These qualities make these solid solutions excellent substitutes
for PmScO3 and EuScO3.
