Correlation between transport properties and lattice effects in the NdCoO3 based catalysts and sensor materials

TL;DR

This paper investigates how the structural and electronic transport properties of NdCoO3 and its doped variants relate, revealing that Ca doping significantly enhances conductivity due to a spin-state transition of Co ions, making it promising for applications.

Contribution

It provides a detailed correlation between lattice effects and transport properties in NdCoO3-based materials, highlighting the impact of doping on spin states and conductivity.

Findings

Ca doping improves room temperature conductivity

Spin-state transition of Co ions explains conductivity changes

Ca-doped NdCoO3 is more suitable for applications

Abstract

This study presents correlations between the structural and transport properties of pure and doped neodymium cobaltate, a compound of great interest for its foreseen applications as catalyst, sensor and thermoelectric material. Neutron and x-ray powder diffraction data have been combined to carefully determine lattice constants and atomic positions and four probe direct current conductivity and thermoelectric power measurements allowed us to follow the thermal evolution of the transport properties of these compounds. The dramatic improvement of the room temperature conductivity of Nd0.8Ca0.2CoO3 with respect to the pure and the Na-doped compound is explained in terms of a different spin-state for the Co ions within this structure. The higher conductivity and the absence of anomalies in the thermal expansion makes the Ca-doped compound more attractive than the pure NdCoO3 in view of possible applications. The experimental data and the Co environment analysis here discussed, in particular bond lengths distortion and bending angles, are fully consistent with a spin state (low to intermediate) transition in NdCoO3