In Situ Studies of Nitridation of Zirconia (ZrO 2 )
2001; American Chemical Society; Volume: 13; Issue: 11 Linguagem: Inglês
10.1021/cm010438d
ISSN1520-5002
AutoresRenu Sharma, Dirk Naedele, Eberhard Schweda,
Tópico(s)Luminescence Properties of Advanced Materials
ResumoThe nitridation of an amorphous ZrO2 ·H2O precursor with gaseous ammonia has been studied by in situ X-ray powder diffraction (temperature range 25−1100 °C), electron diffraction (temperature range 25−800 °C), and electron energy loss spectroscopy (EELS) using a transmission electron microscope equipped with an environmental cell (e-cell). The results show that under the conditions in the e-cell of a transmission microscope (PNH3 = 2 Torr) a cubic nitrogen-containing phase is formed at 820 °C. This phase has low nitrogen content 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 in zirconia, a cubic phase is formed that must be due to the incorporation of nitrogen into the anion lattice. On slow cooling from 1100 °C some superstructure reflections related to the fluorite 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 nitrogen content in the samples; i.e., the color changes from green to yellow to white as the nitrogen content in the sample decreases.
Referência(s)