Sol–Gel Synthesis of Nanocrystalline Antimony-Containing Ceramics from Oxide Precursors

Abstract

In this article, we describe the synthesis of a new oxide pyrochlore containing antimony (V) and bismuth (III) cations, Bi_2.7Ni_0.7Mg_0.46Sb₂O_10+∆ (sp. gr. Fd–3m, a = 10.4703 Å), from a stoichiometric mixture of oxide precursors using a modified sol–gel method (Pechini). It was established that the formation of antimony (III, V) and bismuth (III) compounds, which are volatile upon calcination, can be prevented by dissolving the precursors in sulfuric or nitric acid solutions and excluding the use of hydrochloric acid or chloride solutions. A step-by-step synthesis of two samples in sulfuric and nitric acid media was carried out; the phase composition of the materials calcined in the temperature range of 350 – 950°Ñ was analyzed. The calcination of the sample synthesized in a sulfuric acid solution led to the formation of the Bi_12.67O₁₄(SO₄)₅ phase, which prevented the formation of pyrochlore in the low-temperature region. In the sample synthesized in a nitric acid solution, Bi₃SbO₇ and BiNbO₄ bismuth stibates were recorded as intermediate phases. Sb₂O₄, Bi₁₂MgO₁₉, Bi_7.47Ni_0.53O_11.73, Bi₃Ni_2/3Sb_5/3O₁₁, and NiSb₂O₆ were identified as other intermediate phases. The synthesis temperature of single-phase Bi_2.7Ni_0.7Mg_0.46Sb₂O_10+∆ with a pyrochlore structure was found to be 950°C. The phase purity and chemical composition of the sample were established by XRD analysis and energy-dispersive x-ray spectroscopy (EDS).