Local structure of proton conducting Y-doped AZrO3 (A=Ba, Sr, Ca) perovskites investigated with vibrational spectroscopy

Status: 
Ongoing
Collaborators: 

The International Science Program (Uppsala University, Sweden)

Fuel cells convert chemical energy directly into electrical energy and have an advantage over conventional means of power generation due to their high-energy conversion efficiency besides being environmentally friendly.  The first fuel cell was demonstrated over 160 years ago but development continued inhibited by lack of attractive materials, which have high conductivity in the intermediate temperature region (200-500 ˚C).

This thesis concerns experimental studies done on perovskite structured yttrium doped barium zirconate, calcium zirconate and strontium zirconate systems. The main work has included synthesis of yttrium doped barium zirconate with different Y concentrations and to study the local structure of this system as a function of Y concentration, and to study the influence of protons on the local structure surrounding the Y ions. The experiments were performed using x-ray powder diffraction (XRD), to study the average structure of the perovskite lattice, and infrared (IR) and luminescence spectroscopy to study the local structure of the material.

The results indicate that increasing Y concentration leads to a slight, but clear, distortion of the local structure of the perovskite structure and we also find a dependence on hydration.  Moreover, the results show that the symmetry around the Y atom is more distorted in the dry sample than in the hydrated. For the 20% Y doped BaZrO3 material in particular, spectral differences could not be resolved with the techniques used, which would motivate a further study of the local ordering of the dopant atoms.

Aims:

  1. Synthesize yttrium doped barium zirconate, calcium zirconate and strontium zirconate with different Y concentrations.
  2. Study the local structure of yttrium doped BaZrO3  as a function of Y concentration.
  3. Study the local structure of AZrO3  as a function of A site cation.
  4. Study the influence of hydration on the local structure of the above mentioned materials.
Start Month: 
January
Start Year: 
2008
End Month: 
October
End Year: 
2015

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