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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


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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-ZrO2m-ZrO2 transition indicates that the lack of oxygen in the zirconia lattice favours the formation of metastable t-ZrO2.

Keywords

t-ZrO<sub>2</sub>; m-ZrO<sub>2</sub>; 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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