CERAMICS INTERNATIONAL Available online at www.sciencedirect.com Ceramics International 39 (2013) 8565–8570 Short communication Controlled nucleation and crystal growth through nano SiO 2 for enhancing the orange luminescence of (Sr,Ba) 3 SiO 5 : Eu 2+ in white LEDs application Lei Chen a,d,n , Anqi Luo a , Xinhui Chen a , Fayong Liu a , Erlong Zhao a , Yu Wang a , Yang Jiang a , Zhuofan Yao a , Wenhua Zhang b,1 , Shifu Chen c,2 a School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009, China b National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029, China c Department of Chemistry, Huaibei Normal University, Huaibei 235000, China d Semiconductor and Optoelectronic Technology Engineering Research Center of Anhui Province, Wuhu 241000, China Received 29 January 2013; received in revised form 4 April 2013; accepted 5 April 2013 Available online 18 April 2013 Abstract To enhance the luminescence of (Sr,Ba) 3 SiO 5 :Eu 2+ for white light-emitting diodes, a new method for the synthesis of phosphor was developed. In the proposed method, the mixture of large and nano SiO 2 particles as a silica source was employed to control the nucleation and crystal growth of the material. The impurity phase (Sr,Ba) 2 SiO 4 , which easily coexisted with (Sr,Ba) 3 SiO 5 was suppressed. Accordingly, the luminescence was enhanced significantly by the partial substitution of conventional SiO 2 with nano SiO 2 . The improvement in crystallinity and morphology was examined with XRD and SEM. Moreover, the sintering temperature and the concentration of nano SiO 2 was optimized. The results show that appropriate amount of nano SiO 2 has pronounced effects on the nucleus formation and crystal growth, while excessive crystal seeds formed may hinder the growth of particles. A mechanism for this improvement was proposed. & 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Keywords: Luminescence; Phosphor; Nucleation; Nano SiO 2 ; LED 1. Introduction White light-emitting diodes (WLEDs) show a number of advantages over conventional fluorescent lamps, incandescent bulbs, and cold cathode fluorescent lamp (CCFL) in terms of efficiency, reliability, long lifetime and eco-friendship, which pave way for their wide application in home lighting, outdoor decoration, traffic signal lamps, automobile lights, and the backlights of liquid crystal display (LCD) panels for mobile phones and TV sets, among others [1–6]. However, the WLEDs are mainly fabricated by coating yellow phosphors on blue InGaN chips at present, which have a poor color rendering index (CRI) due to the deficiency of a red component in the emission spectrum. Thus, a red phosphor is desired for improving the CRI of WLEDs [1–6]. (Sr 1−x Ba x ) 3 SiO 4 :Eu 2+ was a promising candidate for the application, whose emission peak could be tuned from about 580 to 600 nm with Ba 2+ concentration varying from x=0 to 0.2 M [7–14]. Recently, several studies have focused on the synthesis and luminescence properties of (Sr,Ba) 3 SiO 5 :Eu 2+ [7–14]. However, the impurity (Sr,Ba) 2 SiO 4 :Eu 2+ easily coex- ists with the formation of (Sr,Ba) 3 SiO 5 :Eu 2+ , which not only decreases luminous efficiency but also deteriorates emission color [11–14]. Wang's research demonstrated that Sr 3 SiO 5 :Eu 2+ tends to decompose into Sr 2 SiO 4 and SrO during the cooling process and the decomposition could be restrained by a rapid cooling speed [11]. In order to enhance luminescence and improve particle morphology, the flux was widely applied in phosphor synthesis. However, the formation of Sr 2 SiO 4 caused by the BaF 2 flux, during Sr 3 SiO 5 synthesis was observed by Cheng et al. [12]. Nakamura et al. has explored the synthesis of www.elsevier.com/locate/ceramint 0272-8842/$ - see front matter & 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved. http://dx.doi.org/10.1016/j.ceramint.2013.04.017 n Corresponding author at: School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009, China. Tel.: +86 551 62901362; fax: +86 551 2901362. E-mail addresses: shanggan2009@qq.com (L. Chen), zhangwh@ustc.edu.cn (W. Zhang), chshifu@chnu.edu.cn (S. Chen). 1 Tel.: +86 551 63602060; fax: +86 551 65141078. 2 Tel./fax: +86 561 3806611.