Preparation, heat treatment and photoluminescence properties of V-doped ZnO–SiO 2 –B 2 O 3 glasses Zohreh Hamnabard a , Zahra Khalkhali b,n , Shamsi Sadat Alavi Qazvini c , Saeid Baghshahi d , Amir Maghsoudipour e a Materials Research School, Ceramic Group, P.O. Box 14395-836, Alborz, Iran b Department of Material Science, Ceramic Division, Iran University of Science and Technology, Tehran, Iran c Faculty of Materials Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran d Faculty of Engineering and Technology, I.K.I. University, Qazvin, Iran e Ceramic Division, Materials and Energy Research Center, Alborz, Iran article info Article history: Received 2 August 2011 Received in revised form 12 December 2011 Accepted 28 December 2011 Available online 4 January 2012 Keywords: ZnO-based scintilator Vanadium Borosilicate glass Photoluminescence Near band edge emission abstract Four glasses in ZnO–SiO 2 –B 2 O 3 ternary system were prepared by the melt quenching method with the objective of optimizing sub-nanosecond emission over the UV region of zinc borosilicate glasses used in superfast scintillators. The effect of vanadium addition and heat treatment on phase formation, microstructure and photoluminescence properties of the glasses was characterized by means of DTA, XRD, SEM and fluorescence spectrophotometer. Vanadium contributed to the near-band-edge emission in two ways, by introducing donor levels in the energy band of ZnO particles and by facilitating the precipitation of ZnO and willemite crystals. Furthermore, nucleation of willemite and zinc oxide phases, which are both the origins of the intense emission bands in the UV region, was facilitated with increasing either the time or temperature of heat treatments. Photoluminescence spectra showed the elimination of the visible emission band which is favorable in scintillating glasses. & 2012 Elsevier B.V. All rights reserved. 1. Introduction As a wide band gap (E g ¼ 3.37 eV) donor semiconductor, ZnO is widely used in scintillating devices. Its two photoluminescence emission bands including a relatively thin band at 380 nm in the UV-region and a relatively wide band at the visible region (500– 600 nm) has so far brought about numerous optical applications for ZnO [1,2]. The visible emission is in the microsecond range and independent of the particle size while the ultraviolet emis- sion is particle size sensitive and of the order of several tens to hundreds of picoseconds and thereby makes ZnO appropriate for superfast scintillators [3]. Glass ceramics have both advantages of glasses and single crystals simultaneously [4] and thus attracted extensive interests in optical applications such as gamma ray detectors, vacuum fluorescent displays [3], light emitting and laser diodes [1], etc. Defects such as uncontrolled distribution of dopants between amorphous and crystalline phases and at their interfaces as a main disadvantage of glass ceramics reduce their optical efficiency [4]. However, researchers reported an improved luminescence efficiency of ZnO embedded in glass compared to that of bulk ZnO [5]. Many techniques, such as sol–gel, impregnation and magnetron sputtering [5], have so far been employed to prepare silicate glasses containing ZnO for application in superfast scintillators. Nevertheless, a few investigations on zinc glasses prepared by the melt quenching method have been conducted as far as we researched in literature. In this work we focused on the photoluminescence dependence to heat treatment temperature and duration in a ZnO–SiO 2 –B 2 O 3 glass system containing different amounts of V 2 O 5 . Vanadium is a high polarizable ion with the atomic refractivity of R a [Ti] ¼ 19 and improves semiconductive properties including PL band by introdu- cing acceptor levels in the band gap of the host matrix [6]. The impact of introducing various amounts of V 2 O 5 on phase forma- tion, microstructure and photoluminescence properties of this glass system is also addressed in this work. Moreover, for deeper understanding of photoluminescence emission mechanism in ZnO- based glasses, a detailed measurement of the optical basicity is included. Optical basicity is a chemical parameter based on the ionic nature of oxides and a more comprehensive approach to the glass composition than the conventional basicity. 2. Experimental procedure Glass specimens were prepared using the conventional melt quenching method according to compositions listed in Table 1. Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/jlumin Journal of Luminescence 0022-2313/$ - see front matter & 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.jlumin.2011.12.083 n Corresponding author. Tel.: þ98 2614320978; fax: þ98 2614464097. E-mail addresses: zhamnabard@nrcam.org (Z. Hamnabard), khalkhali_z@yahoo.com (Z. Khalkhali), IRUH81@yahoo.com (S.S.A. Qazvini), s.baghshahi@ikiu.ac.ir (S. Baghshahi), a_maghsoudi@merc.ac.ir (A. Maghsoudipour). Journal of Luminescence 132 (2012) 1126–1132