Structural evolution and characterization of crystallized luminescent Sr_1-xCa_xWO₄ solid-solution films prepared by an electrochemical method at room temperature

A complete series of well-crystallized solid-solution oxide films, Sr_1-XCa_XWO₄ (0≤X≤1), has been prepared on a tungsten substrate in an electrolytic solution containing Sr²⁺ and Ca²⁺ ions by electrochemical anodization of tungsten substrates at room temperature (25°C). The composition of the solid-solution oxide films was investigated using Vergard's law and x-ray photoelectron spectroscopy. The peak positions of excitation and emission of the films were independent of the Ca content. However, there were variations in the intensities of the emissions: the Ca-rich films showed an extremely strong luminescence, while the Sr-rich films showed a much fainter emission. The crystallization of the films was apparently characterized by three-dimensional nucleation and growth. A model is proposed for the mechanism for formation and growth of the films.