Determination of oxygen stoichiometry in the mixed-valent manganites

TL;DR

This paper discusses a precise redox titration method for determining oxygen content in mixed-valent manganites, highlighting its effectiveness and impact on electrical properties related to oxygen vacancies.

Contribution

It introduces a reliable redox back titration technique for measuring oxygen stoichiometry in manganites, linking oxygen content to electrical transport properties.

Findings

Method is effective and highly reproducible

Oxygen content variation affects electrical transport properties

Oxygen vacancies influence the Mn-O-Mn network

Abstract

The possible redox (oxidation reduction) chemical methods for precisely determining the oxygen content in the perovskite manganites including hole-doped La1-xCaxMnOy and electron-doped La1-xTexMnOy compounds are described. For manganites annealed at different temperatures, the oxygen content of the samples was determined by a redox back titration in which the powder samples taken in a quartz crucible were dissolved in (1+1) sulfuric acid containing an excess of sodium oxalate, and the excess sodium oxalate was titrated with permanganate standard solution. The results indicate that the method is effective and highly reproducible. Moreover, the variation of oxygen content is also reflected in significantly affecting the electrical transport property of the samples, which is mainly considered to be closely related to introduce oxygen vacancies in the Mn-O-Mn network.