ISSN 1087-6596, Glass Physics and Chemistry, 2013, Vol. 39, No. 2, pp. 174–181. © Pleiades Publishing, Ltd., 2013. Original Russian Text © V.A. Aseev, P.A. Burdaev, E.V. Kolobkova, N.V. Nikonorov, 2013, published in Fizika i Khimiya Stekla. 174 INTRODUCTION The creation of the technology of preparation of oxyfluoride glass ceramics was started in the 1970s. An attempt to synthesize oxyfluoride glasses containing Ln 2 O 3 (Ln = Y, La, Gd, Lu, Yb), PbF 2 , and M n O m (M= B, P, Te, Si, Ge) activated by Er 2 O 3 or Tm 2 O 3 was undertaken in [1]. As a result, opaque glass ceramic materials containing microcrystals with a radius of the order of 10 μm having a luminescence efficiency several times higher than that of LaF 3 : Yb : Er reference luminophores. Later, in 1993, the first work on the synthesis of transparent glass ceramics containing a cubic fluoride phase activated by erbium and ytterbium ions was published [2]. Materials com- bining all advantages of aluminosilicate glass matrix with optical characteristics of low phonon fluoride crystals were prepared for the first time. Recently, fluorine-containing transparent glass- crystalline materials activated by REI included in flu- orite like nanocrystalline phases have attracted atten- tion due to a certain set of valuable spectroscopic properties. It is obvious that the optimal materials to create active laser media, luminescent convectors, and luminophores are those which are distinguished by the low frequency phonon spectrum and low content of OH groups because this makes it possible to reduce the losses of excitation through the multiphonon quench- ing process. It was believed for a long time that only fluorine-containing materials (oxygen-free fluoride glasses and crystals) are optimal for solution of the mentioned problem. However, recently, the synthesis of glass-crystalline materials, namely oxyfluoride sili- cate glasses, became a priority direction [3–11]. Such composite materials combine optical parameters of low phonon fluoride crystals with high mechanical, thermal, and chemical characteristics of silicate glasses. It was found that the formation of fluoride nanocrystals activated by REI in the process of heat treatment of an initial glass was possible for some oxy- fluoride glass-like materials. Therefore, the materials obtained combine all the best properties of fluoride nanocrystals influencing optical and spectral-lumi- nescent properties of REI, as well as simplicity of preparation and excellent performance characteristics of oxide glasses (chemical stability, mechanical and thermal strength, optical quality). It is known that minimization of losses due to light absorption and scattering is a critical question when developing opti- cally transparent glass ceramics, including that applied in optical waveguides. The Rayleigh scattering occurring on microinhomogeneities that are close in terms of size to wavelength of the radiation is a limiting factor when using such materials and imposes strict restrictions on the sizes of the separated crystalline phase. According to the concepts of the Rayleigh the- ory, the crystals dispersed in glass should have a radius of no more than 15 nm for the visible region of the spectrum. The difference in values of the refractive index between crystalline phase and an amorphous matrix should not exceed 0.1. These restrictions were subsequently somewhat alleviated. The possibility of preparation of a transparent glass ceramics with nanocrystals having sizes of up to 30 nm and with dif- ference in the refractive indices of no more than 0.3 was demonstrated on the basis of the model [3]. Fluorophosphate Nanostructured Glass Ceramics Activated by Erbium Ions V. A. Aseev a , P. A. Burdaev b , E. V. Kolobkova a , and N. V. Nikonorov a a St. Petersburg State University of Information Technologies, Mechanics, and Optics, Kronverkskii pr. 49, St. Petersburg, 197101 Russia e-mail: kolobok106@rambler.ru b St. Petersburg State Technological Institute (Technological University), Moskovskii pr. 26, St. Petersburg, 190013 Russia Received November 18, 2011 Abstract—Possibility of preparation of transparent nanostructured glass crystalline materials based on fluo- rophosphate glasses with high fluoride content is demonstrated. The influence of concentration of rare earth ions (REI) on the crystallization process is studied. We determined the conditions of heat treatment to form nanocrystals containing REI whose growth is evidenced by the results of X-ray phase analysis changes in the absorption and luminescence spectra and in the lifetime of the excited level of trivalent erbium. Keywords: nanocrystals, glasses, rare earth ions-activators DOI: 10.1134/S108765961302003X