Some Novel Phosphate Phosphors
The need for mercury-free fluorescent lamps for general lighting has become an important subject for light source manufacturers, for avoiding the use of environmentally harmful materials in the lamp. Replacement of conventional fluorescent lamp by light-e
- PDF / 4,002,371 Bytes
- 57 Pages / 439.37 x 666.142 pts Page_size
- 90 Downloads / 247 Views
Some Novel Phosphate Phosphors
7.1 Introduction The need for mercury-free fluorescent lamps for general lighting has become an important subject for light source manufacturers, for avoiding the use of environmentally harmful materials in the lamp. Replacement of conventional fluorescent lamp by light-emitting diodes (LEDs) has been most challenging task in the higher demands for the solid-state lighting technology in recent years. LED technology has flourished for the past few decades. High efficiency, reliability, rugged construction, low power consumption, and durability are among the key factors for the rapid development of the solid-state lighting based on high-brightness visible LEDs [1]. Phosphate has become an important luminescent material for use in LEDs because of their excellent thermal stability and charge stabilization. However, the search for new luminescent materials for plasma display panels (PDPs) and mercury free lamps has been getting increasing attention on the vacuum ultraviolet (VUV, λ < 200 nm) spectroscopic characteristics of rare-earth ions activated phosphors since the last decade [2–6]. The f – f , f –d and charge-transfer transitions of rare-earth ions as well as the host related absorption are the main spectroscopic bands in the VUV range [7, 8]. The f – f transitions of rare-earth ions in the VUV region have been well understood and the Dieke diagram was extended to about 65,000 cm−1 [9]. However, since various factors such as the nature of the coordinating anions, the coordination number, site symmetry and the nature of the next nearest cation neighbors have an influence on the position of the 4f –5d states, a further investigations on the f –d transitions of the rare-earth ions in the different host lattices was necessary [10, 11]. The luminescent properties can be enhanced by adding phosphors with suitable activators. Phosphors with desired colour emission and high efficiency under mercury free excitation must be developed. Recently, some phosphates have been reported, such as LiSrPO4 :Eu2+ [12], NaBaPO4 :Eu3+ [13], BaSrMg(PO4 )2 :Eu2+ [14], NaCa0.98−x Mgx PO4 :Eu2+ 0:02 [15], Na2 CaMg(PO4 )2 :Ce3+ [16]. A detailed literature search reveals no available data for X6 AlP5 O20 (where X = Sr, Ba, Ca and Mg) compounds. This composition can be considered as an K. N. Shinde et al., Phosphate Phosphors for Solid-State Lighting, Springer Series in Materials Science 174, DOI: 10.1007/978-3-642-34312-4_7, © Springer-Verlag Berlin Heidelberg 2013
191
192
7 Some Novel Phosphate Phosphors
alternative approach due to advantages such as lower production cost, simpler manufacture procedure, non-hygroscopic, and environmental-friendly characteristics. The aim of the present work is to investigate the luminescence properties of Dy3+ , Eu3+ and Ce3+ -doped X6 AlP5 O20 (where X = Sr, Ba, Ca and Mg) novel phosphors. The crystalline phosphor phases were synthesized by the combustion method and confirmed by XRD, SEM, and PL spectra of Dy3+ , Eu3+ and Ce3+ . Until now, no crystallographic studies have
Data Loading...
