# Influence of A-Site Deficiency and Ca Concentration on the Electrical and Crystallographic Properties of (Nd0.2Sr0.7–xCax)yTi0.95Fe0.05O3−δ-Based Fuel Electrode for Solid Oxide Cells

## TL;DR

This study examines how A-site deficiency and calcium concentration affect the performance of a fuel electrode material in solid oxide cells.

## Contribution

The study reveals how A-site deficiency and Ca concentration influence microstructure, conductivity, and catalytic activity in a specific fuel electrode material.

## Key findings

- A-site deficiency and Ca concentration significantly impact microstructure, conductivity, and catalytic activity of the electrode.
- The highest electrical conductivity of 4.8 S cm–1 was observed for Nd0.2Sr0.35Ca0.35Ti0.95Fe0.05O3−δ at 850 °C.
- The best electrochemical performance was achieved with a composite of 50% Nd0.2Sr0.25Ca0.45Ti0.95Fe0.05O3−δ and 50% Ce0.9Gd0.1O2−δ.

## Abstract

This study explores the impact of A-site deficiency and
Sr/Ca ratio
on the electrochemical and crystallographic properties of a (Nd0.2Sr0.7–xCax)yTi0.95Fe0.05O3−δ hydrogen electrode for solid
oxide cells under reducing and air atmospheres. 5% and 10% A-site
deficient (Nd0.2Sr0.7–xCax)yTi0.95Fe0.05O3−δ (x = 0.35–0.45, y = 1.05, 1) (referred
to as 5NSCTF-x and 10NSCTF-x) materials
were studied, while the ratio between A-site cations was kept the
same with both deficiencies. The results demonstrate that the extent
of A-site deficiency and the Ca concentration in the A-site have a
significant impact on the microstructure (sinterability), conductivity,
and catalytic activity of electrodes. Segregation of Nd from the lattice
with 5% A-site deficiency was observed as a result of thermal treatment
at low pO2. Among the studied materials, the highest total
electrical conductivity of porous electrode layer at 850 °C and
in 97% H2 + 3% H2O atmosphere was 4.8 S cm–1 observed for the Nd0.2Sr0.35Ca0.35Ti0.95Fe0.05O3−δ (10NSCTF-35). The highest electrochemical performance was observed
in the case of Nd0.2Sr0.25Ca0.45Ti0.95Fe0.05O3−δ (10NSCTF-45),
which showed a polarization resistance value equal to 0.19 Ω
cm2 after 100 h of stabilization at 800 °C in a humidified
(1.7% H2O) H2 atmosphere. The best electrochemical
performance with 606 mW cm–2 power density at 850
°C in 98.3% H2 + 1.7% H2O atmosphere was
demonstrated by a 50 wt % Nd0.2Sr0.25Ca0.45Ti0.95Fe0.05O3−δ + 50 wt % Ce0.9Gd0.1O2−δ composite.