Growth and Investigation of $Nd_{1-x}Sm_{x}ScO_3$ and $Sm_{1-x}Gd_{x}ScO_3$ Solid-Solution Single Crystals

The pseudo-cubic lattice parameters of rare-earth (RE) scandate, $REScO_3$, single crystals grown by the Czochralski technique with RE = Dy to Pr lie between about 3.95 and 4.02 Å. 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, $PmScO_3$ and $EuScO_3$, are, however, not suitable for substrate applications. Because the pseudo-cubic lattice parameters between neighbouring $REScO_3$ compounds decrease with rising atomic number of the RE in about 0.01 Å steps, the unsuitability of $PmScO_3$ (radioactivity) and $EuScO_3$ (incompatibility with Si) causes an interruption in this lattice spacing sequence. To replace them, solid solutions of their adjacent rare-earth scandates, i.e., $(Nd_{0.5}Sm_{0.5})ScO_3$ and $(Sm_{0.5}Gd_{0.5})ScO_3$, were grown by the Czochralski method. Their average pseudo-cubic lattice parameters of 3.9979 Å and 3.9784 Å are very close to those of $PmScO_3$ and $EuScO_3$, respectively, and they show very low segregation. These qualities make these solid solutions excellent substitutes for $PmScO_3$ and $EuScO_3$.