PHASE EQUILIBRIA IN THE MnSb4Te7-MnBi4Te7 SYSTEM AND CHARACTERIZATION OF TETRADYMITE-TYPE LAYERED SOLID SOLUTIONS

Abstract

Phase equilibria and structural evolution in the MnSb4Te7–MnBi4Te7 system were systematically investigated to understand the formation and stability of tetradymite-type layered solid solutions via X- ray diffraction (XRD), differential thermal analysis (DTA), and scanning electron microscopy (SEM) and its T-x diagram was plotted. XRD analysis confirmed that all synthesized MnSb4-xBixTe7 (0 ≤ x ≤ 4) alloys crystallize in a single-phase trigonal structure (P-3m1), with no evidence of secondary phases. The gradual substitution of Sb3+ by the larger Bi3+ ions resulted in a monotonic increase in lattice para- meters which determined via Le Bail method, indicating the formation of a continuous solid solution. SEM imaging further confirmed the homogeneous microstructure of the samples, with no visible phase separation or compositional inhomogeneity. The T-x diagram of system is characterized by peritectic transformations. Due to MnSb4Te7 and MnBi4Te7 melt incongruently, pseudobinary behavior was ob- served only in the subsolidus region. The findings highlight the potential of these solid solutions for de- sired properties, essential for applications in magnetic topological insulators and quantum materials.