Photoluminescence Properties of Eu 3þ Activated CaMoSiO 4 Red Phosphor by Combustion Method Jong Min Kim, Kyung Hwan Kim, Kyung Uk Jang, Sang Joon Park 1 , and Hyung Wook Choi  Department of Electrical Engineering, Kyungwon University, San 65 Bokjeong-dong, Sujeong-gu, Seongnam, Gyeonggi-do 461-701, Korea 1 Department of Chemical Engineering, Kyungwon University, San 65 Bokjeong-dong, Sujeong-gu, Seongnam, Gyeonggi-do 461-701, Korea Received June 25, 2010; accepted October 21, 2010; published online January 20, 2011 The luminescent properties of Eu 3þ doped CaMoSiO 4 red phosphor were investigated. The aim of this work is to investigate the effect of an activator on the luminescent properties of red-emitting CaMoSiO 4 :Eu 3þ phosphor. CaMoSiO 4 :Eu 3þ phosphors were synthesized using a combustion method to obtain small spherical particles that have smooth and round surfaces. Using urea as a fuel and ammonium nitrate as an oxidizer, CaMoSiO 4 :Eu 3þ was successfully synthesized using this combustion method. The Eu 3þ influenced the photoluminescence (PL) spectra of the produced CaMoSiO 4 :Eu 3þ phosphors. The experiment results showed that the strongest emissions occurred with an optimal concentration of the Eu 3þ ; it exhibited a red emission spectrum for near-ultraviolet (UV) excitation. The material would be suited for the fluorescent material used in UV light-emitting diodes (UV-LEDs). The characteristics of the synthesized CaMoSiO 4 :Eu 3þ phosphor were investigated by means of X-ray diffraction (XRD), a scanning electron microscope (SEM), and PL detection. # 2011 The Japan Society of Applied Physics 1. Introduction White light-emitting diodes (LEDs) have drawn much attention due to their valuable applications, such as the backlight source for liquid-crystal displays and power descent lamps. 1) White LED have a better luminescence efficiency compared to incandescent lamps and also pose a challenge for fluorescent lamps. 2) It has become necessary to develop novel, stable and efficient red phosphors for LED applications that can be effectively excited in the near ultraviolet (near-UV) region. In this regard, many red phosphors possessing scheelite, westfieldite, and oxyapatite related structures have been investigated. 3–6) Eu 3þ -doped materials, especially in those where the Eu 3þ ion occupies a non-centrosymmetric site in the host, have been widely used as red-emitting phosphors due to their intense 5 D 0 ! 7 F 2 emission in the red spectral region. Molybdates and tungstates with scheelite structures are considered to be a good host lattice under near-UV or blue excitation due to its MoO 4 tetrahedron unit. Previous investigations have shown that Eu 3þ -doped molybdates and tungstates exhibit a relatively strong absorption in the near-UV region and an intense red emission with a good color purity. 7–10) These results suggest that Eu 3þ -doped molybdates or tungstates may be promising candidates as red-emitting phosphors for LED applications. CaMoO 4 possesses a scheetlite-like (CaWO 4 ) iso-struc- ture; the central Mo 6þ metal ion is coordinated by four O 2 ions in a tetrahedral symmetry (T d ). 11) As reported by Hu et al., CaMoO 4 :Eu 3þ exhibits not only a desirable absorp- tion in the near-UV region, but also excellent thermal and chemical stability. 12) Therefore, CaMoO 4 :Eu 3þ is considered to be a good red candidate that could substitute for the sulfide phosphors in white LEDs. Currently, however, the brightness of CaMoO 4 :Eu 3þ is still inadequate for white LED application. Wang et al. co-doped Sm 3þ , Bi 3þ , and obtained Eu 3þ in molybdate, enhancing the emission intensity of the Eu 3þ . 13) Up until now, there have been few investigations that consider the substitution for the Mo 6þ site. It is well known that the SiO 2 group strongly absorbs the excitation energy in the UV and near-UV regions. 14) Therefore, in order to find efficient red-emitting phosphors that can be applied to near-UV LEDs, CaMoSiO 4 hosts were chosen for the Eu 3þ -ion doping. In this work, to obtain small spherical particles with smooth and round surfaces, we synthesized Eu 3þ activated CaMoSiO 4 phos- phors using a combustion method. 2. Experimental Procedure 2.1 Synthesis In this study, CaMoSiO 4 :Eu 3þ phosphors were prepared using a combustion method. Ca(NO 3 ) 2 (99.997%, Aldrich), MoO 3 (99.99%, Aldrich), SiO 2 (99.9%, Aldrich), and Eu 2 O 3 (99.999%, Aldrich) were used as the starting materials. The CaMoSiO 4 phosphors were doped by Eu 3þ with a molecular formula of Ca 2x Mo 1y Si y O 4 :Eu x 3þ . The Ca(NO 3 ) 2 , MoO 3 , SiO 2 and Eu 2 O 3 were mixed together with a mol ratio and then distilled water was added. Urea was used as the fuel and ammonium nitrate served as the oxidizer. The parameters were measured and are shown in Table I. A flowchart of the preparation of the phosphor powders is shown in Fig. 1. The urea and ammonium nitrate solution was heated to 80  C and continuously stirred using a magnetic bar. The metal solution was dropped into the fuel, and the heating was continued for 30 min. at 80  C. The solution was then transferred to a pre-heated furnace set to 500  C. After heating, different samples of the mixture were sintered in a furnace for 3 h at 600–1200  C. 2.2 Characterization The crystalline development of the resulting samples was checked by X-ray diffraction (XRD; Rigaku D/MAX-2200) using Cu K radiation in the range of 2 ¼ 20{80  . The Table I. The mol ratio of the CaMoSiO 4 :Eu 3þ used by the combustion method at various temperatures. The various mol ratios of the materials Temp.  C Ca 2x Mo 1y Si y O 4 :Eu x 3þ x ¼ 0:02 x ¼ 0:05 x ¼ 0:1 x ¼ 0:2 MoO 3 0.9 600 SiO 2 0.1 800 Urea 20 1000 Ammonium nitrate 20 1200  E-mail address: chw@kyungwon.ac.kr Japanese Journal of Applied Physics 50 (2011) 01BF08 01BF08-1 # 2011 The Japan Society of Applied Physics REGULAR PAPER DOI: 10.1143/JJAP.50.01BF08