Unexpected concentration dependence of Ba2+ dominant substitution in addition to La3+ in cubic Nd3+-doped BaLaLiWO6 perovskites

Abstract

There is a great need in material science to find and investigate new RE3+ ion-doped inorganic materials suitable for producing sintered ceramics of high transparency.Prospective candidates for transparent ceramics should crystalize in highly symmetric crystal systems, so BaLaLiWO6 characterized by a cubic structure (s.g. Fm3¯m) seems to be a good candidate for accomplishing this highly challenging task.A series of micro-crystalline samples activated by Nd3+ ion (0–20 mol%) was produced via the solid-state reaction. Nd3+ ion was chosen as a laser dopant and structural probe. For the first time, the BaLaLiWO6 crystal structure was solved from the single crystal.The originality of this research results from the unexpected substitution of divalent Ba2+ ions by trivalent Nd3+ ones till up to 7 mol% and above this value the replacement of probably both Ba2+ and La3+ ions. Exchange of Ba2+ by Nd3+ ions leads to the formation of cationic vacancies due to the charge compensation effect: 3Ba2+ → 2Nd3+ + □ (vacancy in La3+ cationic sublattice), well-manifested in unit cell expansion with consequences in the spectroscopic characteristics. XRD and SEM methods in combination with emission and absorption spectroscopic ones used at cryogenic temperature helped to determine the substantial properties of this perovskite which could find application in optics. Slightly different cationic positions substituted by the Nd3+ ion and its non-homogeneous arrangement in the Ba2+/La3+ site, detected by spectroscopy with selective excitation under laser at 77 K, is pointed out. The crystal disorder of the cation environment is revealed in broad absorption and emission bands even at low temperature.