INVESTIGADORES
CANEIRO Alberto
artículos
Título:
Phase structure and thermal evolution in coating films and powders obtained by sol-gel process: Part II. ZrO22.5 mole% Y2O3
Autor/es:
R. CARUSO; E. BENAVIDEZ; O. DE SANCTIS; M.C. CARACOCHE; P.C. RIVAS; M. CERVERA; A. CANEIRO; A. SERQUIS
Revista:
JOURNAL OF MATERIALS RESEARCH
Editorial:
MATERIALS RESEARCH SOC
Referencias:
Año: 1997 vol. 12 p. 2594 - 2601
ISSN:
0884-2914
Resumen:
Powders and
coatings of zirconia doped with 2.5 mole% yttria have been produced via the
sol-gel route. The phase structure and subsequent thermal evolution in heating
and cooling cycles have been investigated using mainly perturbed angular
correlations spectroscopy. Thermal analyses and XRD as a function of
temperature have also been performed to obtain complementary information. Upon
heating, the amorphous gels crystallized into the tetragonal structure and
showed the same hyperfine pattern and thermal behavior as observed in
tetragonal zirconia obtained by the ceramic route: the two configurations of
vacancies around zirconium ions denoted as t1 and t2
forms and their mutual t1 → t2
transformation. While the powder sample exhibited an incipient thermal
instability above 1000 °C and underwent completely the t2
form to mZrO2 transition during subsequent, gradual cooling
below 500 °C, the coating retained the tetragonal phase within the whole
temperature range investigated. Hyperfine results suggest that the tetragonal
phase stabilization is favored by the highly defective nature of the t1
form and consequently hardened by the availability of oxygen. The PAC derived
activation energy for the fast diffusion of the oxygen vacancies inherent to
the t2 form was determined as 0.54 ± 0.14 eV.