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Synthesis, Structure, and Luminescence of A2B4C5 Nitrides Vyacheslav Bondar, Lev Axelrud, Vladimir Davydov, Tom Felter1 Ivan Franko Lviv National University, Department of Physics, 50 Dragomanov Str, Lviv, 79005, Ukraine, 1 Lawrence Livermore National Laboratory, PO Box 808, L-356, Livermore, CA, 94550, USA ABSTRACT In order to extend the possibilities of doping of nitrides with activators of different valent and coordination states the complex A2B4C5 nitrides were investigated. The crystallochemical computer simulation of the new phosphor materials based on Mn, Ti and Eu-doped nitrides A2B4C5 has been made. Methods of synthesis of CaSiN2, and MgSiN2 have been developed, and X-ray diffraction analysis of these materials has been carried out. ESR and cathodoluminescent properties of MgSiN2, and CaSiN2 doped with manganese and europium have been studied. INTRODUCTION The usage of GaN-type nitrides with wurtzite structure (AlN, GaN) for creation of RE-doped luminescent materials is limited by possible ways of incorporation of activator atoms in matrix because of persistent valent states of A3B5 matrix and the same for all the matrix atoms tetrahedral coordination. Usage of more complex nitride structures of the type A2B4C52 enables to extend the possibilities of doping of nitrides with different activators. The materials of A2B4C52 class are also known as good semiconductors, however only nitrides of this class have wide band gap, and thus luminescence in visible region of the spectrum can be expected for them [1]. The A2B4C52 nitrides allow formation of several types of structures with substitutions in cation sublattice (А=Mg, Сa, Zn or B=Si, Ge). The results of investigations of CaSiN2, MgSiN2, MgGeN2, and ZnGeN2 compounds are presented in current work. Unlike the A3B5 nitrides, A2B4C52 additionally allow the substitution with atoms of another valent and coordination states as well as allow the introduction of activator atoms into the cavities of layered (MgSiN2) or spaced cross-linked structure (CaSiN2). It allows to expect such type of matrix to be suitable for introduction of various transition or rare-earth luminescent dopants which differ both in size and characteristic coordination. EXPERIMENTAL METHODS The synthesis of nitride compounds was made in several stages. Firstly the synthesis of simple Са3N2 and Mg3N2 nitrides was made by nitriding of metallic Ca or Mg. During the second stage the synthesis of CaSiN2 or MgSiN2 was made from stoichiometric Са3N2 or Mg3N2 with Si3N4. Doping with europium or manganese was made together with synthesis of CaSiN2 and MgSiN2 by adding Eu2O3 or MnC2O4, respectively. The results of synthesis were tested by X-ray diffraction analysis.

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Crystal structure was investigated with X-ray diffractometer HZG-4A with CuKα radiation. X-ray diffraction (XRD) data were measured with step of scanning 0.05° and counting time of 10 sec per point. To determine crystal structure parameters, Rietveld profile refinement method of experimental XRD data analysis was used. The specified p