Original scientific paper

In situ Phase Analysis of the Thermal Decomposition Products of Zirconium Salts

Goran Štefanić ; Ruđer Bošković Institute, P. O. Box 1016, 10001 Zagreb, Croatia
Biserka Gržeta ; Ruđer Bošković Institute, P. O. Box 1016, 10001 Zagreb, Croatia
Stanko Popović ; Department of Physics, Faculty of Science, University of Zagreb, P. O. Box 162, 10001 Zagreb, Croatia
Svetozar Musić ; Ruđer Bošković Institute, P. O. Box 1016, 10001 Zagreb, Croatia

Abstract

X-ray powder diffraction at high temperature was used to determine the phase composition of the thermal decomposition products of two zirconium salts, Zr(SO₄)₂ ⋅ 4 H₂O and ZrO(N0₃)₂ ⋅ 2 H₂O, and of a mixture of zirconium nitrates having Zr(OH)₂(NO₃)₂ ⋅ 4.7 H₂O and ZrO(NO₃)₂ ⋅ 2 H₂O as dominant components. Heating of the samples up to 1200 °C was performed inside a high-temperature chamber, attached to a diffractometer, at an air pressure of ≈ 2 × 10-3 Pa. Regardless of the structural differences in the start-ing salts, thermal decomposition products crystallized to t-ZrO₂, which remained stable up to 1200 °C. This result indicated that the structural nature of the starting materials was not the most important factor of metastable t-ZrO₂ formation. The thermodynamically stable m-ZrO₂ appeared after the cooling of the samples to room temperature. If the cooling was performed at low air pressure, the m-ZrO₂ content was small. Introduction of air, even at RT, caused a considerable increase of m-ZrO₂, which became the dominant phase in ali cases. The important role of oxygen in the t-ZrO₂ → m-ZrO₂ transition indicates that the lack of oxygen in the zirconia lattice favours the formation of metastable t-ZrO₂.

Keywords

t-ZrO₂; m-ZrO₂; X-ray diffraction; in situ phase analysis; phase transitions; lattice defects

Hrčak ID:

132180

URI

https://hrcak.srce.hr/132180

Publication date:

1.9.1999.

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