Effects of paramagnetic interactions by the partial replacement of Zn2+ ions with Cu2+ ions in lead-free zinc-based perovskite (MA)2ZnCl4 crystal by MAS NMR

The growths, structures, phase transition temperatures, and molecular dynamics of mixed (MA)(2)Zn1-xCuxCl4 (x=0, 0.3, 0.5, 0.7, and 1) crystals were investigated to understand the effect of the random presence of paramagnetic Cu2+. In addition, the spin-lattice relaxation time T-1 rho in the rotating frame by the magic angle spinning nuclear magnetic resonance (MAS NMR) method was obtained for H-1 and C-13 nuclei to understand the molecular dynamics for varying amounts of Cu2+ ions. The structure and phase transition temperature for the case where x=0.3 was similar to those for x=0, whereas those of x=0.5 and 0.7 were similar to those for x=1. Although the crystal structures and phase transition temperatures were similar for x (=0 and 0.3), and x (=0.5, 0.7, and 1), the molecular motions of H-1 and C-13 for x=0.3 differed from those for x=0, 0.5, 0.7, and 1. We compared the activation energies Ea by the molecular motions for H-1 and C-13, based on the T-1 rho. The Cu2+ presence for x=0.3 in the mixed structure indicates any differences in the Ea for H-1 and C-13, and the replacement of Zn2+ ions by Cu2+ ions for x=0.3 was strongly affected by the molecular motions. (c) 2019 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).