The effect of oxygen vacancies in Ca1-xSrxHfO3 for x ƒ° 0.25, 0.5 and 0.75

A. LÓPEZ-GARCÍA; R.E. ALONSO; M. FALABELLA; G. ECHEVERRIA

FERROELECTRICS

TAYLOR & FRANCIS LTD

Año: 2010 vol. 396 p. 37 - 48

0015-0193

Solid solutions of SrxCa1-xHfO3 with perovskite structure and nominal composition x = 0.25, 0.50 and 0.75 have been prepared and analysed. The samples were synthesized using the high temperature solid state reaction method. In this condition oxygen vacancies can be produced. The crystalline structure of these samples has been determined by X-Ray Diffraction (XRD) technique and it was observed that all oxides have orthorhombic Pnma spatial group at room temperature. Then, they were irradiated with thermal neutrons to produce the 181Hf-181Ta Perturbed Gamma-Gamma Angular Correlation spectroscopy (PAC) probe. A static, asymmetric and disordered electric field gradient interaction was used to fit the time spectra. The analysis of the hyperfine parameters as a function of composition at laboratory temperature allowed to study the behaviour of different charge distributions in the solid solutions: electrons, cations and oxygen vacancies. The hyperfine quadrupole parameters obtained from the data fit as a function of composition and temperature display discontinuities that are interpreted as crystalline phase transitions at about 900, 850 and 700K, for  x = 0.25, 0.50 and 0.75, respectively.