Nanostructures in calcia stabilized hafnia thin films observed by PAC as a function of temperature

Abstract

The hyperfine quadrupole interaction at Hf sites in films and powders of 14 mol% CaO-HfO 2 and 20 mol% CaO-HfO 2 has been determined as a function of temperature. Results indicate the formation of a cubic solid solution and other microstructures assigned to the φ 1 (CaHf 4 O 9 ) and φ 2 (Ca 6 Hf 19 O 44 ) phases. Dynamical effects on the electric field gradient reveal the existence of oxygen vacancies movements in the solid solution. The thermal behavior of the relaxation constant observed in films allowed the determination of activation energies of 0.54 eV and 0.70 eV for the 14 mol% and 20 mol% CaO doped hafnias, respectively. The influence of the microdomains and the stability of the cubic solid solution are discussed.

Phase evolution in the mechanochemical synthesis of stabilized nanocrystalline (ZrO2)0.97(Y2O3)0.03 solid solution by PAC technique

“…Details of the atomic arrangements of materials of technological uses were studied using short range methods as extended X-ray absorption fine structure (EXAFS) [22] and the perturbed angular correlations (PAC) [23,24] techniques. In particular, PAC technique has proved to be an efficient tool in the investigation of the milling effect of the monoclinic zirconia by showing the quadrupole interactions of special atomic arrays through which the monoclinic phase transforms into the tetragonal form [25].…”

A short and long range study of mullite–zirconia–zircon composites

“…The existence of regions of aperiodic domains has been reported in some ceramic materials only when investigated by such short range techniques as perturbed angular correlations (PAC) [3,4] or extended X-ray absorption fine structure (EXAFS) [5]. The PAC method [6], in particular, has proved to be an efficient tool in the investigation of zirconia-based ceramics because it allows the determination of different atomic configurations around zirconium sites, hardly resolvable by other techniques.…”