Microelectrodes have a number of advantages over macroelectrodes for quantitative electroanalysis and monitoring, including reduced iR drop, a high signal-to-noise ratio and reduced sensitivity to convection. Their use in molten salts has been generally precluded by the combined materials challenges of stresses associated with thermal cycling and physical and corrosive chemical degradation at the relatively high temperatures involved. We have shown that microfabrication, employing high precision photolithographic patterning in combination with the controlled deposition of materials, can be used to successfully address these challenges. The resulting molten salt compatible microelectrodes (MSMs) enable prolonged quantitative microelectrode measurements in molten salts (MSs). This paper reports the fabrication of novel MSM disc electrodes, chosen because they have an established ambient analytical response. It includes a detailed set of electrochemical characterisation studies which demonstrate both their enhanced capability over macroelectrodes and over commercial glass pulled microelectrodes, and their ability to extract quantitative electroanalytical information from MS systems. MSM measurements are then used to demonstrate their potential for shedding new light on the fundamental properties of, and processes in, MSs, such as mass transport, charge transfer reaction rates and the selective plating/stripping and alloying reactions of liquid Bi and other metals; this will underpin the development of enhanced MS industrial processes, including pyrochemical spent nuclear fuel reprocessing.

The 6-layered hexagonal polymorph of BaCrO 3 has been synthesized at 900°C under a pressure of 9 GPa. The hexagonal structure (space group P6 3 /mmc, cell parameters a = 5.3809(9) and c = 13.123(3) Å at 300 K) is stable on cooling down to 5 K. Ferrimagne-

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The 6‐layered hexagonal polymorph of 6H‐BaCrO3 is prepared by hot isostatic pressing of Ba3Cr2O8 (from BaCO3 and Cr2O3, 1000 °C, 12 h) and Cr2O3 in the molar ratio of 2:1 (multianvil press, 900 °C, 9 GPa, 30 min).