title: Synthesis and characterization of metastable β-Ag2WO4: an experimental and theoretical approach.
abstract: Metastable silver tungstate (β-Ag2WO4) has attracted much attention lately because of its many potential applications. However, the synthesis of metastable phases of inorganic compounds is challenging because of the ease of transformation to the stable phase. We have overcome this challenge and have successfully synthesized β-Ag2WO4 microcrystals using a dropwise precipitation (DP) method in aqueous media at low temperature. The microcrystals were characterized by X-ray diffraction (XRD), including powder X-ray diffraction structural determination, field-emission scanning electron microscopy (FE-SEM), and micro-Raman/ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy. To complement the experimental data, we present first-principles quantum-mechanical density functional theory (DFT) calculations. Using XRD data, Raman/UV-vis data, and the determined optical band gap, together with geometric optimization calculations, we confirmed the structure of this compound. β-Ag2WO4 has a hexagonal structure with a P63/m space group. The building blocks of the lattice comprise two types of W-O clusters, [WO4] and [WO5], coordinated to four and five O atoms, respectively, and two types of Ag-O clusters, [AgO6], and [AgO5], linked to six and five O atoms, respectively. This type of fundamental study, combining multiple experimental methods and first-principles calculations, helps to obtain a basic understanding of the local structure and bonding in the material.
authors.affiliation: DQ-Universidade Federal de São Carlos, P.O. Box 676, CEP, 13565-905 São Carlos, São Paulo, Brazil.
authors.forename: Pablo S
authors.initials: PS
authors.lastname: Lemos
authors.affiliation: Institute of Crystallography-CNR, Via G. Amendola 122/o, 70126 Bari, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Altomare
authors.affiliation: DQ-Universidade Federal de São Carlos, P.O. Box 676, CEP, 13565-905 São Carlos, São Paulo, Brazil.
authors.forename: A F
authors.initials: AF
authors.lastname: Gouveia
authors.affiliation: Instituto Federal do Maranhão, PPG em Engenharia de Materiais, 65025-001, 65030-005, São Luís, MA, Brazil.
authors.forename: I C
authors.initials: IC
authors.lastname: Nogueira
authors.affiliation: CDMF-Universidade Estadual Paulista, P.O. Box 355, 14801-907, Araraquara, SP, Brazil and University Jaume I, Department of Analytical and Physical Chemistry, 12071 Castellon, Spain. andres@qfa.uji.es.
authors.forename: L
authors.initials: L
authors.lastname: Gracia
authors.affiliation: University Jaume I, Department of Analytical and Physical Chemistry, 12071 Castellon, Spain. andres@qfa.uji.es.
authors.forename: R
authors.initials: R
authors.lastname: Llusar
authors.affiliation: University Jaume I, Department of Analytical and Physical Chemistry, 12071 Castellon, Spain. andres@qfa.uji.es.
authors.forename: J
authors.initials: J
authors.lastname: Andrés
authors.affiliation: DQ-Universidade Federal de São Carlos, P.O. Box 676, CEP, 13565-905 São Carlos, São Paulo, Brazil and CDMF-Universidade Estadual Paulista, P.O. Box 355, 14801-907, Araraquara, SP, Brazil.
authors.forename: E
authors.initials: E
authors.lastname: Longo
authors.affiliation: DQ-GERATEC-Universidade Estadual do Piauí, João Cabral, N. 2231, P.O. Box 381, 64002-150 Teresina, PI, Brazil.
authors.forename: Laécio S
authors.initials: LS
authors.lastname: Cavalcante