On the controversial formation of silver diboride: Processing of Ag + 2B powders by spark plasma sintering

Following recent theoretical studies based on electronic structure calculations conducted on Ag- and Au-borides which estimated their superconducting behaviour at elevated transition temperatures, the preparation of AgB₂ was attempted in this work by reactive Spark Plasma Sintering (SPS) from Ag and B elemental powders. It was found that, independently from the processing conditions adopted, the formation of a new phase, which corresponds to a small peak on the XRD pattern at 2θ equal to about 28°, cannot be attributed to AgB₂. In fact, it was shown that the new phase detected on sintered pellets is most likely boric acid which is formed only if the sample is left in contact with air. If SPSed samples were stored under inert (Ar) atmosphere, no additional phases other than unreacted elements were observed.