Contents lists available at ScienceDirect Journal of Luminescence journal homepage: www.elsevier.com/locate/jlumin Hydrothermal synthesis of CdWO 4 for scintillator-polymer composite films development S.M.V. Novais a, ⁎ , T.J. Monteiro a , V.C. Teixeira b , M.A. Gomes a , M.E.G. Valerio a , Z.S. Macedo a , L.B. Barbosa a a Physics Department, Federal University of Sergipe, São Cristóvão, SE, Brazil b Brazilian Synchrotron Light Laboratory, Brazilian Center for Research in Energy and Materials, Campinas, SP, Brazil ARTICLE INFO Keywords: CdWO 4 Polystyrene Composite Luminescence Microtomography ABSTRACT Composite films of CdWO 4 embedded in polystyrene have been prepared and characterized through micro- tomography, photoluminescence and X-ray excited optical luminescence. CdWO 4 scintillator powder was suc- cessfully produced via microwave-assisted hydrothermal method using oxide precursors. With the control of synthesis pH, CdWO 4 wolframite structure was obtained at temperatures as low as 100 °C for reaction time of 1 h. Surface modification of CdWO 4 particles by stearic acid promoted good dispersion of scintillator nano- particles within the polymeric matrix. The composites have been prepared with 220 μm or 440 μm thickness and CdWO 4 /PS mass ratios of 10% and 20%. Optical measurements show the characteristic CdWO 4 emission in the blue region as well as PS luminescence due to PPO, POPOP and PTO organic impurities. Under X-ray excitation, the light output was proportional to the increase of scintillator content and sample thickness. The emission intensity varied for each film face irradiated, being the most homogeneous condition achieved for the composite of 440 μm and CdWO 4 /PS = 10%. 1. Introduction Scintillator compounds are continuously investigated for improving their potential applications which include medical image detectors, dosimetry and industrial inspection. Besides the features of efficiency, decay time and chemical stability, it is also important to achieve low costs of production especially when large areas need to be covered [1,2]. In this sense, systems based on inorganic particles embedded in polymeric matrix are shown to be promising since they can combine the mechanical features of polymers with the optical properties of scintil- lators. These organic/inorganic composites have thus aroused great interest in recent years as inexpensive and efficient detectors for io- nizing radiation [3–6]. The use of a material with high effective atomic number Z will in- crease the stopping power, that is, the absorption of high energy ra- diation by the composite in comparison with the polymer without such particles [7,8]. In many cases, energy transfer between these elements take place, with the luminescent properties of the composite de- termined by these processes. On the other hand, one of the main issues that need further attention is the control of the particles dispersion within the polymeric matrix. Particle clusters can act as scattering centres, which compromise the spatial resolution of the detectors, whereas low amounts of scintillator result in decrease of the lumines- cence efficiency [8,9]. Cadmium tungstate (CdWO 4 ) is a well-known scintillator due to its useful features such as high density (7.9 g/cm 3 ), large Z (61.2) and efficient scintillation output (~40% of NaI:Tl). Owing to the difficulties to obtain CdWO 4 as single crystals, many other synthesis routes have been developed to produce polycrystalline samples including sol-gel, sonochemical and hydrothermal [10–13]. Up to our knowledge, however, few reports have explored the ability to prepare composites loaded with this compound [14]. The search for new scintillating films is relevant since the convenience of using as the primary radiation sensor in many detection systems, including synchrotron radiation facilities [15,16]. In this work, scintillator composites have been prepared using CdWO 4 and polystyrene (PS). The advantages of using PS consist on its low cost, good resistance to thermal and light deterioration, flexibility and high transparency over a large spectra range [1,17]. The synthesis of CdWO 4 powder employed a simple microwave-assisted hydrothermal method, which allowed the formation of single crystalline phase at temperatures as low as 100 °C. Our approach involves the surface modification of the particles in order to improve their compatibility with the polymeric matrix and achieve a higher homogeneity of the composite films [18]. https://doi.org/10.1016/j.jlumin.2018.03.056 Received 1 December 2017; Received in revised form 15 March 2018; Accepted 20 March 2018 ⁎ Corresponding author. E-mail address: suellen.mvn@gmail.com (S.M.V. Novais). Journal of Luminescence 199 (2018) 225–231 Available online 21 March 2018 0022-2313/ © 2018 Elsevier B.V. All rights reserved. T