Gadolinium ion localization in RbPb2Cl5 crystals

Abstract

1.As a result of the search for new materials for solid state diode pumped lasers operating in the mid infrared region at room temperature, a family of low symmetry crystals of double halides of an alkali metal and lead APb 2 Cl 5 (where A = K, Rb) was found. These crystals feature chemical stability, low hygroscopicity, narrow phonon spectrum, and possible activation by rare earth ions.The space group of these crystals is P2 1 /c (P12 1 /c1); according to [1,2], the APb 2 Cl 5 structure contains two inequivalent lead ion sites with triclinic symmetry (C 1 ). The nearest environment of one site (Pb2 in the notation of [1]) is a "tricapped" trigonal prism with a coordination number (CN) of 9 (Fig. 1a). The other site (Pb1) is in the distorted bicapped octa hedron (CN = 7). In [3], as a result of the study of the KPb 2 Cl 5 structure, it is proposed to represent the envi ronment of these two lead sites (Pb2, Pb1) as bicapped (due to remoteness of one of ligands) (CN = 8) and monocapped (CN = 7) trigonal prisms. The authors of [4] attribute only six chlorine ions with R < 0.3 nm to the nearest environment of Pb1 in KPb 2 Cl 5 and con sider the coordination number of Pb2 to be equal to 7 ("umbrella" of five chlorine ions with R ≈ 0.3 nm and two ions with distances of 0.315 and 0.321 nm). Taking into account the ratio of ionic radii and charge states of a rare earth element, lead, and rubidium, it can be expected that exactly the lead site will be substituted with rare earth ions.The authors of the optical study of KPb 2 Cl 5 :Nd 3+ [4] and measurements of the high frequency EPR of Tb 3+ ions in KPb 2 Cl 5 [5] assume that rare earth ions are mostly localized at Pb1 sites. In this case, in [5], it was considered that the substitution of lead at the site Pb1 with the Tb 3+ ion is accompanied by the forma tion of a vacancy of one of the nearest K + ions.The authors of [6] studied RbPb 2 Cl 5 with dyspro sium and bismuth impurities in order to determine localization of rare earth ions and mechanisms of their charge compensation using broadband EPR spectroscopy. These measurements did not allow a final conclusion about the Dy 3+ localization in RbPb 2 Cl 5 .2. In the same samples (RbPb 2 Cl 5 :1.0 wt % DyCl 3 ), we detected an EPR spectrum of high spin (S = 7/2) rare earth Gd 3+ ion (Fig. 2), existing in the crystal as an uncontrolled impurity (<0.01%). The single crys tals under study were grown by the Bridgman method in quartz ampules [7]. Measurements were performed using a Bruker EMX Plus spectrometer operating in the 3 cm range at room temperature.As seen in Fig. 2, the spectrum of Gd 3+ centers is well described by the strong magnetic field approxima tion. The weak satellites observed near seven allowed (Δm = 1, m is the electron spin projection) transitions can be caused by both sample mosaicity and twinning. Similar satellites are observed in other magnetic field orientations. The orientation behavior of the positions of the main spectrum transitions in three crystallo graphic planes is shown in Figs. 3-5. Splittin...

Comparison of EPR spectra of the Gd3+ ion‐doped YAl3(BO3)4, EuAl3(BO3)4, and TmAl3(BO3)4 single crystals

“…However, even for isovalent replacement an impurity ion distorts the local environment. Such distortions can be determined by analyzing the spectrum changes with axial and all‐round pressure or by using an empirical superposition model, which has shown its adequacy in the analysis of local distortions created by impurity ions .…”

EPR study of the ground state of Mn2+impurity ions in alumoboratesMAl3(BO3)4(M= Y, Eu, Tm)

“…The purpose of this work was to study the EPR spectra of Mn 2+ ions in the isomorphous series of aluminum borates YAl 3 (BO 3 ) 4 , EuAl 3 (BO 3 ) 4 and TmAl 3 (BO 3 ) 4 in a temperature range of 4.2-290 K to find out how the variation of lattice parameters influences the EPR spectrum in crystals, and what are the temperature changes of static and dynamic characteristics of the spectrum. An attempt was made to analyze the features of the spectra using an empirical superposition model that was previously used in the analysis of local distortions of impurity ions [18][19][20][21][22][23][24].…”