Low temperature controllable synthesis of transition metal and rare earth borides mediated by molten salt

Abstract

Transition meal and rare earth borides have been subjected to extensive investigations because of their unique structures, superior properties and diverse applications. Conventional methods for their syntheses suffer from various drawbacks. So several alternative approaches have been explored. Among them, the so-called ‘molten salt synthesis (MSS)’ technique has proved promising. Over the past 10–15 years, it has been used to prepare a range of transition metal and rare earth borides. In this paper, the main results from these studies are reviewed. Initially, the relevant background on metal borides and their conventional synthesis methods are introduced, followed by the main principles/mechanisms of MSS. The following three sections provide an overview of the main work on MSS of binary and ternary borides, boride solid solutions, and boride-based composite powders. Then, two newly modified MSS approaches are presented. Finally, the main issues covered in this paper are summarised, and future prospects considered.