| Abstract
| - The nitridation of an amorphous ZrO2 ·H2O precursor with gaseous ammonia has beenstudied by in situ X-ray powder diffraction (temperature range 25−1100 °C), electrondiffraction (temperature range 25−800 °C), and electron energy loss spectroscopy (EELS)using a transmission electron microscope equipped with an environmental cell (e-cell). Theresults show that under the conditions in the e-cell of a transmission microscope (PNH3 = 2Torr) a cubic nitrogen-containing phase is formed at 820 °C. This phase has low nitrogencontent with no superstructure reflections, confirming the absence of anion/vacancy ordering.X-ray diffraction results under an ammonia partial pressure of 760 Torr show that at 1100°C, 500 °C below the usual temperature for the tetragonal to cubic phase transition inzirconia, a cubic phase is formed that must be due to the incorporation of nitrogen into theanion lattice. On slow cooling from 1100 °C some superstructure reflections related to thefluorite structure have been observed, on account of the ordering of the anion/vacancies.The EELS data show that the color of the samples can be related to the overall nitrogencontent in the samples; i.e., the color changes from green to yellow to white as the nitrogencontent in the sample decreases.
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