resumo
Phase pure sample of the microporous copper silicate CuSH-1Na has been obtained by simplified hydrothermal method without using additives (H2O2 and Na2HPO4). Ion exchange of Na+ by Cs+, Ca2+ and Sr2+ ions showed that the structure can suffer partial replacement of the charge compensating cations. Ion exchange with Cs+ resulted in distinct dehydration while the ion exchange with Sr2+ increased the total amount of water. Water content in the Ca-exchanged sample is comparable to the as-synthesized sodium phase. Raman spectroscopy revealed that the divalent cations as Ca2+ and Sr2+ induce stronger local structural deformations than the monovalent Cs+. These structural changes have been also followed by the refined lattice distortions. Magnetic analyses showed that CuSH-1Na presents a very weak ferromagnetic interaction along the Cu2+ chains with a nearly vanishing Curie-Weiss temperature. This magnetic coupling is associated with super-super-exchange interactions through Cu-Na-O-Na-Cu paths. Antiferromagnetic coupling, attributed to inter-chains super-super-exchange interactions, competes with the ferromagnetic one and prevails at the lowest temperature.
palavras-chave
CRYSTAL-STRUCTURE; TITANIUM-SILICATE; OPEN-FRAMEWORK; HYDROTHERMAL SYNTHESIS; MAGNETIC-STRUCTURES; ZEOLITE FRAMEWORK; TITANOSILICATE; EXCHANGE; PURIFICATION; ETS-10
categoria
Chemistry; Materials Science
autores
Lopes, AML; Lin, Z; Ferdov, S
nossos autores
Zhi Lin
Investigador Principalagradecimentos
This work was supported by the Portuguese Foundation for Science and Technology (IF/01516/2013 and IF/00686/2014).