Lanthanide Ions Research Paper

1. INTRODUCTION

1.1 BACKGROUND AND MOTIVATION

In the recent years, an extensive advancement in the field of phosphors has been bloomed by deliberately introducing trivalent rare earth ions (lanthanides) as luminescent centers (dopants) in different host matrices to produce rare earth activated phosphors for lighting applications. A phosphor literally, light bearer is a material capable of absorbing energy and re-emitting it in the form of light (ultra violet, visible or Infrared). In general, Most of the phosphors are usually made up of a host material (matrix) and dopant. The host material is normally an insulator or a semiconductor with a wide band gap and it serves to accommodate the dopant. The host also controls some of the physical properties

Thus, in general 4f orbitals do not participate in bonding and the optical properties of these ions are relatively insensitive to the environment, e.g. coordinated ligand, host lattice and so on. The incomplete occupation of shielded 4f shell is the reason of fascinating luminescence properties of lanthanide ions, with many of them showing very sharp lines. These lines originate from the intra-configurational [Xe] 4fn → [Xe] 4fn transitions and was intensively studied in the recent years. Luminescent properties of rare earth ions together with a maximum number of available transitions ranging from the deep ultra violet to the mid infrared make them suitable candidates for optical applications. Moreover, besides line emission some of the rare earth ions also possess broad band due to [Xe] 4fn → [Xe] 4fn−1 5d1, and charge-transfer (CT) transitions. The energy levels of the lanthanide ions in a range of crystals were extensively investigated and tabulated by Dieke and co-workers in 1968.An intensive research on rare earth activated phosphors led to invention of fluorescent lamps, color television, plasma

This review presents a thorough survey of earlier published works on crystal structure, size distribution and optical properties of the rare earth ions activated molybdate, and tungstate based phosphor materials for lighting applications.

3. Experimental This chapter deals with the materials, preparation technique and instrumentations in detail. The list of the starting compounds required for the synthesis of phosphors is given. Mechanochemically assisted SSM reaction at room temperature method was employed for the synthesis of phosphors have been illustrated in detail and also the devices used for the characterization of the phosphor materials have been discussed. These devices are such as luminescence spectroscopy, XRD studies, energy dispersive X-ray analysis, Infrared (IR) spectroscopy, scanning electron microscopy and Raman spectroscopy.

4. Synthesis and photoluminescence properties of CaMoO4: x Eu3+ phosphors

CaMoO4: x Eu3+ nano phosphors have been successfully prepared by mechanochemically assisted SSM reaction route at room temperature. The characteristics of the europium doped red phosphor materials were analyzed in detail using XRD, Fourier Transform infrared spectroscopy, scanning electron microscope and photoluminescence(PL) and diffuse reflectance spectroscopy in