When we dope the perovskite having ABO3 type structure with metal ion, which factors decide whether A site is substituted or B site is substituted by dopant metal ion ?
Hi, Shobhita,
It depends on the ionic radii of A and B in ABO3 and ionic radius of dopant. Ionic size of the dopant must be comparable to the ionic size of cation of A- or B-site at which you want to dope.
If the ionic radius of the additive ion is compatible with the ionic radius of A site, it will likely replace it with high probability. This is the same for B site. If it is compatible with both sites (A and B), you can check the valances of ions. If the valences are also compatible, the crystal field energies will help you on this.
As mentioned by Volkan, ionic radii will be something to check for. You might also want to check literature for the coordination environments preferred by the dopant. In an ideal perovskite structure, A sites has 12 fold coordination and the B site will have 6 fold coordination. Usually A sites are occupied by the alkali earth metals like Ca, Sr, Ba or Lanthanides (La,Pr e.t.c) and B sites by transition metal ions.
Please check the attached file and check the following websites :
- https://www.webelements.com/periodicity/ionic_radius/
- http://abulafia.mt.ic.ac.uk/shannon/ptable.php
Dopant will substitute either A site or B site depending on its resemblance to the ionic radii of A or B. If ionic radii of dopant is very close to ionic radii of A then A site will be substituted, if it is very close to B then B site will be substituted.
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