Template-engaged solid-state synthesis of barium–strontium silicate hexagonal tubes

Abstract

Solid materials with hollow structures are of significant interest due to their beneficial features, such as a high surface to volume ratio, high void space in the structure, and low apparent density, allowing such applications as high efficiency catalysts and drug delivery agent. This study presents a new synthetic method for generating hexagonal hollow tubes of (BaSr)SiO4 via a template-engaged solid–solid reaction. First, the composition tuneable (BaSr)CO3 hexagonal rods were prepared as the template by the co-precipitation of Ba2+, Sr2+, and then uniformly shelled with the silica (SiO2) using CTAB, thereby forming (BaSr)CO3–SiO2 core–shell rods. The SiO2 shell thickness is adjustable based on the TEOS concentration in the sol–gel process. The (BaSr)CO3–SiO2 core–shell rods were converted to the (BaSr)SiO4 hexagonal hollow tubes by an interfacial solid–solid reaction between the (BaSr)CO3 core and SiO2 shell at 750 °C. During this interfacial solid–solid reaction, the (BaSr)CO3 hexagonal rods are the template for hexagonal tubes of (BaSr)SiO4. Kirkendall effect contributes to the formation of hollow tube structure of (BaSr)SiO4. The proposed synthetic method demonstrated a significant advantage for the preparation of (BaSr)SiO:Eu2+ phosphor, where the synthetic temperature was reduced from 1200 °C to 500 °C when compared with the conventional method. The photoluminescence property of the hollow tubular (BaSr)SiO:Eu2+ showed a green emission between 480 nm and 600 nm with the maximum peak intensity at 517 nm under UV excitation. This synthetic method could also be applied to the preparation of hollow-structured multi-component metal silicates.