Local structural investigation of Ca & Sr doped LaAlO3 perovskite

Abstract

In this work, Lanthanum aluminate (LaAlO3), La0.8Ca0.2AlO3 (LCAO) and La0.8Sr0.2AlO3 (LSAO) have been prepared by high energy ball milling with different ball milling hours (25hours,50hours,75 hours and 100 hours) to study the local distortion in lattice due to presence of dopants (Ca and Sr).We used simple materials lanthanum oxide (La2O3)(99.98%) Sigma-Aldrich),aluminum oxide(Al2O3)(99% Sigma- Aldrich),calcium oxide(CaO) and strontium carbonate(SrCO3) to create this powders, we heated it at 900°C to complete the process. It was characterized by several techniques: X-ray diffraction (XRD), Field-emission Scanning Electron Microscope (FESEM), LCR meter, thermogravimetric and differential thermal analysis (TG/DTA). X-ray diffraction (XRD) confirmed that LaAlO3 samples changing their phase from hexagonal to cubic structure slowly with increasing ball milling hours and Ca doped LaAlO3 shows existence of secondary phase(unwanted impurity CaCO3) which play vital role in dielectric measurement. Field-emission Scanning electron microscopy (FESEM) reveals very fine clusters of nanosized spherical particles and the product is highly agglomerated with increasing ball milling hours. Dielectric constant of LaAlO3 is found to be 30-12. The dielectric property depends on this local atomic arrangement of Ca and Sr atoms in LaAlO3 and coexistence of multiple phases. A tiny amount of dopant (like Sr or Ca) can significantly change how materials work, including their electrical conductivity and dielectric constant. We will study how the LaAlO3 powder changes as the particle size gets smaller and then connect the dielectric properties to the structure at the nano- scale since electronic devices are becoming more miniaturized.