Synthesis and crystal chemical evolution of fresnoite powders

(Ba,Sr)2TiSi2O8 fresnoite powders were prepared via a Pechini process in which citric acid and ethylene glycol were used as complexing agents. The resulting gel contained a homogeneous distribution of the metal ions that suppressed the formation of (Ba,Sr)TiO3 perovskite as a secondary phase during calcination. Phase development was examined as by isochronal and isothermal reaction analysis. A combination of thermo- and differential gravimetric analysis (TGA–DGA), quantitative X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) confirmed that calcination at 900 °C/12 h yielded finely crystalline (∼70 nm) Ba2TiSi2O8 (BTS) and Sr2TiSi2O8 (STS). The endmembers and compositional intermediates crystallized directly from the Pechini resin and indirectly through reaction of (Ba,Sr)CO3, (Ba,Sr)TiO3 and a silica-rich glass intermediates. This new method for preparing fresnoite yields materials suitable for consolidation as dense monolithic dielectrics or for use as high surface area catalytic powders.

Graphical abstractThe Pechini synthesis of (Ba, Sr)2TiSi2O8 titano-silicate fresnoites delivers finely divided precursors for applications as diverse as solid electrolytes and photocatalysis that exploit the unique Ti–O and Si–O bonding and structural morphology of these materials.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► A Pechini method for synthesizing (Ba,Sr)2TiSi2O8 fresnoites is demonstrated. ► The method minimizes a persistent glassy intermediate phase. ► The Pechini process is generally applicable for tailoring fresnoites as functional materials.