Journal of Alloys and Compounds 395 (2005) 227–230 Preparation of Y 3 Al 5 O 12 :Cr powders by microwave-induced combustion process and their luminescent properties Yen-Pei Fu a,∗ , Shen Tsao b , Chen-Ti Hu b a Department of Chemical Engineering, Wu-Feng Institute of Technology, Ming-Hsiung, Chiayi 621, Taiwan b Department of Materials Science and Engineering, National Tsing-Hua University, Hsinchu 300, Taiwan Received 4 October 2004; accepted 25 October 2004 Available online 11 January 2005 Abstract A novel ceramic synthesis technique, microwave-induced combustion process was investigated for the production of Y 3 Al 5 O 12 :Cr powders with improved physical and luminescence properties. This technique involves the reaction of aluminum nitrate (Al(NO 3 ) 3 ·9H 2 O), yttrium nitrate hexahydrate (Y(NO 3 ) 3 ·6H 2 O), chromium nitrate (Cr(NO 3 ) 3 ·6H 2 O), and carbohydrazide (CO(N 2 H 3 ) 2 ) at microwave-oven and the whole process took only 30 min. The powders of Y 3 Al 5 O 12 :Cr were further investigated by X-ray diffractometer (XRD), infrared spectroscopy (IR), and photoluminescence excitation and emission spectra (PL). The results showed that the formation temperature of YAG phase is significant low, compared to solid-state reaction route of constituent oxides. For luminescence property, the emission intensity of YAG:Cr powders synthesized by microwave-induced combustion increases gradually with Cr amount. © 2004 Elsevier B.V. All rights reserved. PACS: 74.25.Gz; 74.62.Bf; 78.55.Hx Keywords: YAG; Microwave-induced combustion; Luminescence 1. Introduction Inorganic luminescence materials are crystalline com- pounds that absorb energy and subsequently emit this ab- sorbed energy as light [1]. Phosphors are composed of an inert host lattice and an optically excited activator, typically a 3d or 4f electron metal such as Ce 3+ , Cr 3+ , Eu 3+ , and Tb 3+ . Oxide phosphors were found to be suitable for field emission display (FED), vacuum fluorescent display (VFD), electro- luminescent (EL) devices, and plasma panel display (PDP) devices. Y 3 Al 5 O 12 (YAG) is an advanced ceramic with interesting optical and mechanical properties [2,3]. YAG is a refractory, hard oxide ceramic that does not damage easily under con- dition of high irradiance with an electron beam. Moreover, YAG doped with a lanthanide element can be widely used as solid-state laser material in the luminescence field and as ∗ Corresponding author. Tel.: +886 5 226 9281; fax: +886 5 226 9281. E-mail address: ypfu@mail.wfc.edu.tw (Y.-P. Fu). window material for a variety of lamps [4–6]. Because YAG- based phosphors have high temperature chemical stability, they are expected to replace sulfide-based materials, which are currently used as main components in cathode ray tube (CRT) [7]. YAG and YAG-based phosphors have been prepared by several techniques, such as solid-state reaction [8,9], sol–gel [10], coprecipitation method [11,12], and hydrother- mal method [13]. In this study, we used a new method called microwave-induced combustion to synthesise YAG:Cr pow- der. Microwave processing of materials is fundamentally dif- ferent from conventional processing in terms of the heat gen- eration mechanism. In a microwave oven, heat is generated within the sample itself by interaction of microwaves with material. In conventional heating, heat is generated by heat- ing elements and then transferred to the sample surfaces [14]. Microwave-induced combustion synthesis involves the dissolution metal nitrate and carbohydrazide in water [15], and then heating the resulting solution in a microwave oven. After the solution reaches the point of spontaneous combus- 0925-8388/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2004.10.071