The role of rare earth elements and Mn(2+) point defects on the luminescence of bavenite.

Natural fibrous crystals of bavenite (Ca(4)Be(2)Al(2)Si(9)O(26)(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 Gd(3+) (319nm), Sm(3+) (562 and 594nm), Dy(3+) (572nm) and Tb(3+) (495nm). A Mn(2+) band at about 578nm in Ca(2+) sites is present as a broad band that overlaps with the Dy(3+), Sm(3+) and Tb(3+) bands. Mn(2+) is a transition metal ion that has an electron configuration of 3d(5) and interacts strongly with the crystal field (d --> d) transition. Stability tests at different temperatures show clearly that the TL glow curves at 400nm 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 = 29.7ppm, Dy = 22.7ppm, Sm = 9.45ppm, Nd = 8.95ppm and Gd = 8.15ppm in the bavenite lattice.