Investigation of the Nd$_2$O$_3$--Lu$_2$O$_3$--Sc$_2$O$_3$ phase diagram for the preparation of perovskite-type mixed crystals NdLu$_{1-x}$Sc$_x$O$_3$

TL;DR

This study maps the phase diagram of the Nd2O3--Lu2O3--Sc2O3 system, identifying primary crystallization fields and successfully growing mixed NdLuO3--ScO3 perovskite crystals using melt methods.

Contribution

It provides the first detailed thermodynamic assessment of the Nd2O3--Lu2O3--Sc2O3 system and demonstrates crystal growth of mixed perovskite crystals from the melt.

Findings

Four primary crystallization fields identified.

Crystals of NdLuO3--ScO3 mixed perovskite successfully grown.

Thermodynamic assessment aids in crystal synthesis planning.

Abstract

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.