Phase formation in the Ag2MoO4–Rb2MoO4–Hf(MoO4)2 system

Abstract

Systematic studies of the subsolidus structure of ternary molybdate systems allow expanding the representation of ternary molybdates. In this paper we studied the solid phase interaction in the Ag2MoO4–Rb2MoO4–Hf(MoO4)2 system for the first time using X-ray phase analysis. To determine the quasi-binary sections, we use the method of “intersecting cuts”. It helped to reveal the formation of new Rb5Ag1/3Hf5/3(MoO4)6 and Rb3AgHf2(MoO4)6 phases. We also determined their thermal characteristics using differential scanning calorimetry. The ternary molybdate Rb5Ag1/3Hf5/3(MoO4)6 crystallised in the trigonal syngony with the following unit cell parameters: a = 10.7117(1), c = 38.5464(5) Å (space group R3с, Z = 6). The Ag2MoO4–Rb2MoO4–Hf(MoO4)2 system is characterised by the existence of ten quasi-binary cross sections. The experimental data obtained in this work complement the information on phase equilibria in condensed ternary systems containing molybdates of tetravalent elements and two different monovalent elements. This provides opportunities for the combination of the compositions of ternary molybdates due to cationic substitutions, which will allow controlling their properties.

Keywords

• phase diagram
• triangulation
• solid-state synthesis
• ternary molybdate
• silver molybdate
• rubidium molybdate
• hafnium molybdate
• x-ray diffraction analysis