The role of rare earth elements and Mn2+ point defects on the luminescence of bavenite

Natural fibrous crystals of bavenite (Ca4Be2Al2Si9O26(OH)2) collected in intra-granitic pegmatite bodies of Bustarviejo (Madrid, Spain) have been examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), electron microprobe (EMPA) and inductively coupled plasma-mass spectrometry (ICP-MS). The strong luminescence emissions of bavenite using thermoluminescence (TL), cathodoluminescence (CL) and its thermal stability have been recorded, looking for new physical properties and new phosphor or dosimetric uses. The bavenite luminescence takes place in the 5d electron shell that interacts strongly with the crystal field; the spectra bands assignment are Gd3+ (319 nm), Sm3+ (562 and 594 nm), Dy3+ (572 nm) and Tb3+ (495 nm). A Mn2+ band at about 578 nm in Ca2+ sites is present as a broad band that overlaps with the Dy3+, Sm3+ and Tb3+ bands. Mn2+ is a transition metal ion that has an electron configuration of 3d5 and interacts strongly with the crystal field (d → d) transition. Stability tests at different temperatures show clearly that the TL glow curves at 400 nm in both irradiated and non-irradiated bavenite samples track the typical pattern of a system produced by a continuous trap distribution. The ICP-MS analyses show concentrations of Yb = 29.7 ppm, Dy = 22.7 ppm, Sm = 9.45 ppm, Nd = 8.95 ppm and Gd = 8.15 ppm in the bavenite lattice.