Structural phase transitions and stress accommodation in (La0.67Ca0.33MnO3)1−x:(MgO)x composite films
Year: 2002
Type: article
Abstract: Composite $({\mathrm{La}}_{0.67}{\mathrm{Ca}}_{0.33}{\mathrm{MnO}}_{3}{)}_{1\ensuremath{-}x}:(\mathrm{MgO}{)}_{x}$ films were prepared by metalorganic aerosol deposition on a (100)MgO substrate for different concentrations of the (MgO) phase $(0<~x<~0.8).$ At $x\ensuremath{\approx}0.3$ a percolation threshold in conductivity is reached, at which an infinite insulating MgO cluster forms around the ${\mathrm{La}}_{0.67}{\mathrm{Ca}}_{0.33}{\mathrm{MnO}}_{3}$ grains. This yields a drastic increase of the electrical resistance for films with $x>0.3.$ The film structure is characterized by x-ray diffraction and transmission electron microscopy. The local structure of the ${\mathrm{La}}_{0.67}{\mathrm{Ca}}_{0.33}{\mathrm{MnO}}_{3}$ within the film depends on the MgO concentration which grows epitaxially along the domain boundaries. A different structural phase transition from the orthorhombic Pnma structure to an unusual rhombohedral $R3\ifmmode\bar\else\textasciimacron\fi{}c$ structure at the percolation threshold $x\ensuremath{\approx}0.3$ is found for ${\mathrm{La}}_{0.67}{\mathrm{Ca}}_{0.33}{\mathrm{MnO}}_{3}.$ A three-dimensional stress accommodation in thick films through a phase transition is suggested.
Language: English
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2004402293