ISSN 0020-1685, Inorganic Materials, 2014, Vol. 50, No. 2, pp. 197–204. © Pleiades Publishing, Ltd., 2014. Original Russian Text © N.V. Lichkova, V.N. Zagorodnev, A.G. Okhrimchuk, L.N. Butvina, D.V. Irzhak, V.K. Karandashev, 2014, published in Neorganicheskie Materialy, 2014, Vol. 50, No. 2, pp. 215–222. 197 INTRODUCTION Advances in the growth of high-purity and rare- earth-doped crystals of double salts with the general formula MPb 2 Hal 5 (M = K, Rb; Hal = Cl, Br) and investigation of their luminescence spectra suggest that such crystals can be used for creating solid-state lasers emitting in the mid-IR spectral region. KPb 2 Cl 5 crystals doped with Nd 3+ , Dy 3+ , and Er 3+ ions were reported to lase near 1.06, 2.4, and 4.6 μm, respec- tively [1–3]. Okhrimchuk et al. [4] were the first to demonstrate lasing in a RbPb 2 Cl 5 :Dy 3+ single crystal, with a nonhygroscopic crystalline host, at a wave- length of 5.5 μm at room temperature. These results suggest that crystals of lead halide-based double salts are new, potentially attractive gain media for solid- state lasers emitting in the mid-IR spectral region. Availability of crystals with high optical quality and high rare earth concentration is critical for the ability to produce efficient solid-state light sources based on the MPb 2 Hal 5 double salts. The use of isomorphous substitutions in the MPb 2 Hal 5 double salts probably will allow one to obtain crystals of variable composi- tion with tailored functional properties. Isaenko et al. [5] studied the properties of mixed-cation crystals of K x Rb 1 – x Pb 2 Br 5 double salts. The structure of the crys- tals was shown to influence the key features of the Er 3+ distribution in them, and the composition of the solid solution of the double salt was determined in which the Er 3+ concentration was sufficient for efficient lasing. The objectives of this work were to examine the possibility of preparing high-purity and praseody- mium- and dysprosium-doped double and mixed salts with the general formula Rb 1 – x M x Pb 2 Cl 5 – y Br y (M = K, Cs) and assess the effect of isomorphous substitutions of potassium and cesium cations for rubidium cations and bromine anions for chlorine anions on the struc- ture of crystals of the solid solutions and the behavior of Pr 3+ and Dy 3+ impurities in them. EXPERIMENTAL High-purity and praseodymium- and dysprosium- doped solid solutions between double and mixed salts based on lead halides were prepared by an integrated process proposed previously: quenching of appropri- ate molten mixtures under an inert atmosphere [6]. The phase composition of the quenched stoichio- metric mixtures was determined by differential ther- mal analysis (DTA) using an MOM Q-1500 D ther- moanalytical system (Hungary). The stoichiometric mixtures obtained were used as charges for the crystal growth of the solid solutions and mixed salts. The growth charges were doped with Preparation of Pr- and Dy-Doped Rb 1 – x M x Pb 2 Cl 5 – y Br y (M = K, Cs) Crystals N. V. Lichkova a , V. N. Zagorodnev a , A. G. Okhrimchuk b , L. N. Butvina b , D. V. Irzhak a , and V. K. Karandashev a a Institute of Microelectronics Technology and High Purity Materials, Russian Academy of Sciences, ul. Akademika Osip’yana 6, Chernogolovka, Moscow oblast, 142432 Russia b Fiber Optics Research Center, Russian Academy of Sciences, ul. Vavilova 38, Moscow, 119333 Russia e-mail: lichkova@ipmt-hpm.ac.ru Received January 30, 2013 Abstract—We have demonstrated for the first time the possibility of preparing high-purity and praseody- mium- and dysprosium-doped solid solutions based on lead halides and alkali metals: Rb 1 – x Cs x Pb 2 Cl 5 , Rb 1– x Cs x Pb 2 Br 5 , Rb 1– x K x Pb 2 Cl 5 , and RbPb 2 Cl 5– y Br y . According to X-ray diffraction data, Rb 1  x Cs x Pb 2 Cl 5 and Rb 1– x Cs x Pb 2 Br 5 crystals in the solid solution range are isostructural with the constitu- ent double salts RbPb 2 Cl 5 and RbPb 2 Br 5 , respectively. The double salt Rb 0.5 K 0.5 Pb 2 Cl 5 is isostructural with KPb 2 Cl 5 , and the double mixed salt RbPb 2 Cl 2.5 Br 2.5 is isostructural with RbPb 2 Br 5 . The Pr 3+ and Dy 3+ con- centrations in crystals of the solid solutions and mixed salts were determined by inductively coupled plasma mass spectrometry (ICP-MS). In the Rb 1– x (Cs, K) x Pb 2 Hal 5 (Hal = Cl, Br) solid solutions, the dopants were observed to be nonuniformly distributed over the host. According to ICP-MS analysis data and absorption spectra, the Pr 3+ and Dy 3+ concentrations in the RbPbCl 2.5 Br 2.5 crystals were higher than those in RbPb 2 Br 5 . DOI: 10.1134/S0020168514020101