Mechanisms of the formation of a surface phase with the matrix composition in a Ca2Nb2O7 single crystal

Creating dual-mode luminescence in piezoelectric calcium niobates through lanthanide-doped for anti-counterfeiting and temperature sensing

“…1d indicates the reflection spectra of phosphor powders doped with praseodymium and erbium prepared by solid-phase reaction. What can be summarized from the figure that is the reflected light of all specimens has a significant decrease around 279 nm, which is due to the valence band to the conduction band in the Ca2Nb2O7 matrix lattice absorption [30]. In addition, there are three absorption bands between 300 and 650 nm, which are located at 460, 530, and 610 nm, respectively.…”

“…1b. The prepared specimen's system belongs to monoclinic P21 space group, and the oxygen octahedron is formed by six oxygen octahedron around Nb atoms in calcium niobate crystal [30]. The SEM result of the prepared ceramic sheet sample is shown in the Fig.…”