Reaction of sodium chromate with zirconium under vacuum and high temperature

•The mechanism of Na2CrO4 reduction by Zr under high-temperature vacuum conditions was elucidated.•The reduction of Na2CrO4 by Zr depended on the activation level of the Zr surface.•Zirconium reduces chromium oxide to metallic Cr at elevated temperatures. In this study, the reaction mechanism of sodium chromate (Na2CrO4) with zirconium (Zr) under vacuum and high temperature was investigated using X-ray diffraction and X-ray photoelectron spectroscopy. The degree of Zr activation increases with increasing temperature. Na2CrO4 is initially reduced to NaCrO2 at temperatures above 600 °C. NaCrO2 decomposed spontaneously, and sodium vapor was formed as the temperature increased. Interestingly, metallic chromium (Cr) was detected at high temperatures, possibly due to the reduction of chromium oxide by zirconium. The results clearly illustrate the reduction mechanism, as the temperature increases, the Zr surface is activated and Na2CrO4 is reduced to NaCrO2 by Zr. Subsequently, NaCrO2 is gradually decomposed into Na vapor and Cr2O3, and finally Cr2O3 is reduced to Cr metal and ZrO2 by Zr.