Peculiar Structural Effects in Pure and Doped Functional Single Crystals of Complex Compositions

Abstract

Results of a detailed structural characterization of nominally pure and doped single crystals of scheelite, eulytin, and perovskite families obtained by melt methods were considered and analyzed. The influence of growth and post-growth annealing conditions on actual compositions of crystals is shown. The reasons for the coloration of the crystals are explained. A change in crystal symmetry due to crystal–chemical and growth reasons is considered. The use of structural analysis and X-ray absorption spectroscopy is substantiated to reveal the role of activator ions in the formation of statistical and local structures, respectively. A relationship between the distribution of activator ions over crystallographic sites and photoluminescent parameters of materials is established, which allows selecting optimal systems for the application. The combined results of studying single-crystal compounds of other classes (huntite, sillenite, whitlockite, garnet, tetragonal bronzes) allow formulating and summarizing structural effects that appeared in the systems and caused by various factors and, in many cases, due to the local environment of cations. A principal difference in the structural behavior of solid solutions and doped compounds is shown. The methodology developed for single-crystal samples of complex compositions can be recommended for the systematic structural studies of functional materials of different compositions.

Revealing the peculiar local behavior of manganese and cobalt in diffusion-doped calcium orthovanadate Ca3(VO4)2

“…32 It is known that the method of dopant introduction affects the actual composition and features of defect formation in crystals and hence their functional properties. 33,34 The aim of this work is to determine statistical and local structures, in particular, types and concentrations of point defects as well as crystallographic positions, local environments, and formal charges of dopant ions in Czochralski-grown Ca 3 (VO 4 ) 2 single crystals doped with manganese and cobalt introduced by the diffusion from Mn 2 O 3 and Co 3 O 4 solid phases. Structural features are comprehensively studied by single-crystal and powder synchrotron X-ray diffraction and conventional single-crystal X-ray diffraction as well as by X-ray absorption spectroscopy.…”

Effect of lattice disorder on charge transfer in lead molybdate crystals

“…Exposure to irradiation leads to the appearance of photoinduced phenomena, such as photochromic and photodielectric effects [1]. X-ray diffraction, luminescence, and EPR studies have shown that the crystal lattice of such crystals contains point and extended defects, various clusters, including photoinduced ones, based on anionic MoO 4 groups that have captured photoelectrons [2,3]. In fact, PbMoO 4 single crystal is a partially disordered medium.…”