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Monolithic t ‐ZrO 2 Nanopowder through a ZrO(OH) 2 · x H 2 O Polymer Precursor
Author(s) -
Mondal Aparna,
Ram Shanker
Publication year - 2004
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.2004.tb07489.x
Subject(s) - materials science , monoclinic crystal system , endothermic process , amorphous solid , tetragonal crystal system , crystallite , nanoparticle , nucleation , analytical chemistry (journal) , crystallography , crystal structure , chemistry , nanotechnology , adsorption , organic chemistry , metallurgy
Monolithic t ‐ZrO 2 (tetragonal structure) nanopowder is synthesized with an amorphous ZrO(OH) 2 · x H 2 O polymer precursor. The H 2 O molecules impart the structure and promote reconstructive thermal decomposition of the structure to t ‐ZrO 2 nanoparticles on heating at temperatures as low as 200°C. A prevalent endothermic heat output in the dissociation process controls the local temperature in exothermic nucleation and growth of various groups of the reaction species so that it is self‐controlled in high‐energy nanoparticles. Crystallites are, on average, d = 8 nm diameter, and they have a high value of Gibbs free energy or lattice volume V o = 0.06770 nm 3 . The excess volume decreases to V o = 0.06705 nm 3 if the reaction temperature is increased to >200°C, i.e., approximately the bulk value of 0.06681 nm 3 ; there is a minor increase to d = 12 nm at 600°C. Many oxygen vacancies in the thin surface space‐charge layers seem to support the stability of small particles in this particular polymorph. A pure m ‐ZrO 2 (monoclinic structure) appears with d = 22 nm at temperature as low as 800°C. The results are analyzed using X‐ray diffractometry, microstructure, infrared spectroscopy, and thermal studies of the polymer precursor and derivative t ‐ZrO 2 nanoparticles.