QUASIBINARY SECTIONS FORMATIO IN THE Ag – Sb – P – Se SYSTEM
Authors: Sabov V.I. , Barchii I.E. , Piasecki M. , Filep M.J. , Pogodin A.I. , Sabov M.Yu. 
Published: September 2022

The possibility of combining different properties of materials within Ag – Sb – P – Se system prompted the study of the nature of physicochemical interactions in it. The main attention was paid to systems based on AgSbP2Se6 with the participation of stable binary and ternary compounds. It was assumed that the cross sections involving stable compounds would be quasi-binary. However, the nonquasibinarity of the sections Ag2Se – AgSbP2Se6 and Ag7PSe6– AgSbP2Se6 was proved, which indicated a complex interaction in the Ag – Sb – P – Se system. Difficulties were caused by the formation in the process of synthesis of multicomponent mixtures, the determination of the phase composition of which was complicated by the presence of reflexes on the powder patterns of different phases at the same angles. In this regard, it was expedient to summarize the experimental data on the nature of physicochemical interactions in the cross sections of the Ag – Sb – P – Se system. This would allow the establishment of quasi-binary, quasi-ternary and quasi-quaternary systems within the Ag – Sb – P – Se system, which was the aim of this work.
It was established the nonquasibinarity of Ag7PSe6 – AgSbP2Se6 system. It intersects two quasi-ternary systems Ag4P2Se6 – AgSbSe2 – Se and Ag4P2Se6 – Sb2Se3 – Se. Other samples consist four-phases, in each of which, in addition to three complex compounds, selenium was detected. The quasiternary and quasiquaternary systems were formed by following quasibinaries: Ag7PSe6 – Ag4P2Se6, Ag7PSe6 – AgSbSe2, Ag7PSe6 – Se, Ag4P2Se6 – AgSbSe2, Ag4P2Se6 – Se, AgSbSe2 – Se, Ag4P2Se6 – Sb2Se3, AgSbSe2 – Sb2Se3, Sb2Se3 – Se, AgSbP2Se6 – Ag4P2Se6, AgSbP2Se6 – Sb2Se3, AgSbP2Se6 – Se.
In the study of the cross section Ag2Se – AgSbP2Se6 it was found that it is also not quasi-binary and intersects one quasi-ternary (Ag7PSe6 – AgSbSe2 – Ag) and one quasi-binary system (Ag4P2Se6 - AgSbSe2). However, it is not taken into account that the Ag2Se – AgSbP2Se6 system also intersects the Ag4P2Se6 – Sb2Se3 system, which is quasi-binary. A refining analysis of the data confirmed that the cross section of Ag2Se - AgSbP2Se6 intersects the above quasi-ternary and two quasi-binary systems. In addition to the identified twelve, the study of the nature of the interaction in the cross sectionAg2Se – AgSbP2Se6 confirmed the quasibinarity of four systems (Ag7PSe6 – Ag2Se, Ag2Se – Ag, Ag2Se – AgSbSe2 and Ag – AgSbSe2) and additionally a system AgSbP2Se6 – Sb4(P2Se6)3.
Thus, were established seventeen quasi-binary sections. It should be noted that some of them were known in the literature. Ag2Se – Ag and Sb2Se3 – Se systems are partial of the Ag – Se and Sb – Se systems, respectively, the Ag2Se – AgSbSe2 and AgSbSe2 – Sb2Se3 systems are subsystems of the quasi-binary Ag2Se – Sb2Se3 system. So, by fact thirteen quasi-binary systems in the quaternary system are established.
It is noteworthy that the quaternary compound AgSbP2Se6 does not form quasi-binary systems with silver-containing complex compounds. The exception is Ag4P2Se6, which is often the final, occasionally intermediate product of the interaction of AgSbP2Se6 with other silver-containing compounds.