Solid state 47,49Ti, 87Sr and 137Ba NMR characterisation of mixed barium/strontium titanate perovskites

Abstract

Solid state 47,49Ti, 137Ba, 87Sr NMR spectra have been recorded on Ba x Sr 1− x TiO 3 (0 ⩽ x ⩽ 1) perovskite samples prepared by the powder sintering method. Multinuclear solid state NMR shows great potential for characterising such systems since the quadrupolar parameters are very sensitive to any geometric deformation around the studied nucleus. 47,49Ti NMR powder lineshapes appear strongly influenced by the presence of even a small amount of barium (or strontium) in the coordination second sphere of the probed titanium site: substitution of strontium by barium induces the broadening of the peaks, due to quadrupolar effects, while the isotropic chemical shift increases. 137Ba NMR spectra exhibit a distribution of the quadrupolar interaction, that could be tentatively quantified, C Q increasing with the amount of strontium. Preliminary results were also obtained on 87Sr NMR showing behaviour comparable to 137Ba NMR, i.e. a broadening of the peaks due to an increasing quadrupolar interaction with the amount of barium distorting the environment of the strontium sites.