Different Roles of Ce³⁺ Optical Centers in Oxyorthosilicate Nanocrystals at X-ray and UV Excitation

• Main Authors: Vladyslav Seminko, Pavel Maksimchuk, Iryna Bespalova, Yuri Malyukin
• Format: Article
• Language: English
• Published: MDPI AG 2019-02-01
• Series: Crystals
• Subjects: cerium; luminescence; lutetium silicate; yttrium silicate; nanocrystals
• Online Access: https://www.mdpi.com/2073-4352/9/2/114

Luminescence properties of Lu₂SiO₅:Ce³⁺ and Y₂SiO₅:Ce³⁺ nanocrystals were studied using photo- and X-ray luminescence techniques. The crystal structure of Re₂SiO₅ nanocrystals (P2₁/c space group) differs from the crystal structure of Re₂SiO₅ bulk crystals (C2/c space group) with 9- and 7-oxygen-coordinated cation positions instead of 6- and 7-coordinated ones observed for Re₂SiO₅ bulk crystals. Two optical centers (Ce1 and Ce2) were observed for Re₂SiO₅:Ce³⁺ nanocrystals originating from cerium ions substituting 9- and 7-oxygen-coordinated cation sites. Preferential substitution of larger cation sites by cerium ions leads to higher photoluminescence intensity of Ce1 centers, however, Ce2 centers are the main centers for electron-hole recombination, so only Ce2 band is observed in X-ray luminescence spectra. The features of oxygen coordination of Ce1 and Ce2 centers and high content of oxygen vacancies in Re₂SiO₅:Ce³⁺ nanocrystals can provide preferential trapping of electrons near Ce2 centers, and therefore, the dominant role of Ce2 band in X-ray luminescence spectra.