New triple molybdate Rb₂AgIn(MoO₄)₃: synthesis, framework crystal structure and ion-transport behaviour

Area of Science:

• Solid State Chemistry
• Materials Science
• Crystallography

Background:

• Molybdate compounds are known for their diverse structural and functional properties.
• The exploration of ternary systems involving alkali metals, silver, and trivalent metals can lead to novel materials.
• Ionic conductivity in solids is crucial for applications like solid-state batteries and sensors.

Purpose of the Study:

• To synthesize and characterize a new triple molybdate in the Rb₂MoO₄-Ag₂MoO₄-In₂(MoO₄)₃ system.
• To determine the crystal structure of the newly discovered compound.
• To investigate the ionic conductivity and phase transition behavior of the synthesized material.

Main Methods:

• Solid-state reactions and spontaneous crystallization from melts were employed for synthesis.
• Single-crystal X-ray diffraction was used to determine the crystal structure.
• Impedance spectroscopy was utilized to measure electrical conductivity.

Main Results:

• A new triple molybdate, Rb₂Ag_1+3xIn_1-x(MoO₄)₃ (x ≉ 0.004), was synthesized and its structure determined in the R-3c space group.
• The structure features a 3D framework of (In,Ag)O₆ octahedra and Ag1O₆ trigonal prisms, with additional Ag2O₆ prisms facilitating 2D ionic conductivity.
• The compound undergoes a phase transition at 535 K, with electrical conductivity reaching 1.1 × 10^-2 S cm^-1 at 720 K.

Conclusions:

• The novel Rb₂Ag_1+3xIn_1-x(MoO₄)₃ possesses a unique crystal structure conducive to ionic transport.
• The material demonstrates significant ionic conductivity at elevated temperatures.
• This compound holds potential for applications requiring high ionic conductivity in demanding thermal environments.