Thermal expansion behaviour of Sr- and Mg-doped LaGaO3 solid electrolyte

Thermal expansion coefficients (TECs) of Sr- and Mg-doped LaGaO3 were measured continuously from room temperature up to 1000 °C. It was observed that TECs increased with the increase in dopant concentration. In the continuous TEC curve depression due to a structural change from orthorhombic to rhombohedral of the material was also observed. It was found that at a given Sr content varying the amount of Mg content led to an increase in the phase transformation temperature whereas the reverse was found to be true with the increase in Sr content. The thermal expansion was found to increase with increasing oxygen vacancies irrespectively of the type of the dopant responsible for causing the vacancy. This increase was attributed to the weakening of the binding energy as a result of the creation of additional oxygen vacancies.