Date on Master's Thesis/Doctoral Dissertation

12-2019

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Chemistry

Degree Program

Chemistry, PhD

Committee Chair

Ramezanipour, Farshid

Committee Co-Chair (if applicable)

Noble, Mark

Committee Member

Noble, Mark

Committee Member

Maurer, Muriel

Committee Member

Yu, Ming

Author's Keywords

solid state chemistry; solid state materials; magnetic structure; electrical properties; electrocatalytic activity; conductivity

Abstract

The present thesis deals with the synthesis and study of the physico-chemical properties of perovskite based oxide materials. Several novel oxygen deficient perovskites (ODP) have been synthesized by conventional solid state synthesis method. The novel compounds are CaSrFe2O6-δ, CaSrFeCoO6-δ, Ca2Fe1.5Ga0.5O5, CaSrFeGaO5 and BaSrFe2O5. Their magnetic, charge transport and electrocatalytic properties have been studied. Structural effect on electrical conductivity, magnetic and electrocatalytic properties have been studied in some series of ODPs. CaSrFe2O6-δ, CaSrFeCoO6-δ, Ca2Fe1.5Ga0.5O5 and CaSrFeGaO5 have brownmillerite type orthorhombic structures with layered structure having alternate tetrahedral and octahedral layers which are connected to one another by corner sharing. These are vacancy ordered compounds. BaSrFe2O5 is vacancy disordered compound with cubic structure. Most of the studied materials exhibited G-type long range antiferromagnetic arrangement of magnetic moments. During the study of charge transport property, compounds with structural order in a particular series show relatively less conductivity at room temperature and semiconductive nature and transition to metallic conductivity during temperature dependent conductivity measurement. Vacancy disordered compounds show relatively higher conductivity at room temperature and show mixed (semiconductive and metallic) conductivity during temperature dependent conductivity measurement. The study of electrocatalytic properties revealed the relation with the conductivity and the structural order. The electrocatalytic activity toward oxygen evolution reaction is highly efficient if the material is highly conductive or highly ordered.

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