Synthesis and characterization of ACrO2 (A=Cu, Ag) delafossite compounds

Abstract

The field of multiferroics has become more important for both: a basic understanding of the interaction between magnetic and electric coupling and the potential use of such materials in technical devices. Although there are many magnetic and ferroelectric materials, there are relatively few choices for multiferroic materials, since the conditions for co-existence of several types of order are stringent. Recent discovery of multiferroicity and p-type conductivity in delafossite compounds finds a potential application in transparent semiconductor devices. Hydrothermal synthesis of AgCrO2 delafossite was difficult to prepare at low temperature (<230 °C) in an aqueous solution. Cu and Ag based delafossite compounds generally require high process temperature and exhibit minor impurity phases prepared via other conventional methods. Furthermore, very few reports are available for magnetic cation substitution study in CuCrO2 system. Thus, in the search of a new multiferroics, new ACrO2 (A= Cu, Ag) delafossite compounds were prepared by hydrothermal, solid state and monomode microwave (MW) method. CuCrO2 prepared by MW heating proved to be the fastest method compare to conventional methods. Study of vanadium substituted CuCr1-xVxO2 (0 ≤ x ≤ 0.5) compounds prepared by solid state reaction method showed spin glass state for higher vanadium substituted samples (0.2 ≤ x ≤ 0.5) and remains long range antiferromagnetic ordered system for lower vanadium substituted samples (0 ≤ x < 0.2). Hydrothermal method was developed to obtain AgCrO2 polycrystalline sample in supercritical water condition using K2Cr2O7 as an oxidizing agent. Also, hydrothermal method was developed to obtain Ag-based photocatalysts. Thus, after a successful growth of pure CuCrO2 and AgCrO2 delafossite, hydrothermal process can be used to grow the single crystal of these compounds which is a basic block of fabrication of highly efficient transparent optoelectronic devices, microelectronics, spintronics, and sensors.