Sol-gel synthesis and structure of cordierite/tialite glass-ceramics

In the present work the results of the research on the sol-gel synthesis and structure of cordierite (2MgO·2Al2O3·5SiO2), tialite (Al2O3·TiO2) and cordierite/tialite glass-ceramics as well cordierite containing 2 wt.% of Co and Co+Cu have been described and discussed. The sol-gel synthesis was carried out using different kind of precursors as follows: Al(NO3)×9H2O, Si(OC2H5)4 , Ti(OC4H9)4 , Mg(NO3)2×6H2O, chlorides or nitrates of corresponding metals, H2O, C2H5OH, Aqua Regia, NH4F and PEG. The synthesized gels were dried and thermally treated in the temperature range from 800°C to 1200°C. The sol-gel processes and structure of the cordierite, tialite and cordierite/tialite glass-ceramics have been investigated by means of XRD, FTIR, TEM, SEM and EPMA

Dielectric properties of bismuth titanate ceramics containing SiO2 and Nd2O3 as additives

Bismuth-titanate ceramics containing SiO2 and Nd2O3 as additives are synthesized by melt quenching method in the system Bi2O3-TiO2-Nd2O3-SiO2 in the temperature range of 1250–1500 °C. The phase composition of the obtained materials is determined by X-ray diffraction analysis and energy dispersive spectroscopy. Using scanning electron microscopy different microstructures are observed in the samples depending on the composition. Different values of conductivity, dielectric losses and relative permittivity are obtained depending on the composition. It is established that all investigated samples are dielectric materials with conductivity between 10^-9 and 10^-13 (Ω·cm)^-1 at room temperature, dielectric permittivity from 1000 to 3000 and dielectric losses tgδ between 0.0002 and 0.1

Sol-gel synthesis and structure of La2O3–CoO–SiO2 powders

LaCoO3 powders are studied because they exhibit interesting electrical, magnetic and catalytic properties. In this paper, new synthesized La2O3-CoO-SiO2 powders with different quantity of silica were prepared via solgel method in aqua media, starting from metal nitrates with different chelating agents. The relation between the reaction in solution, crystallization pathway and morphology were discussed. In LaCoO3-SiO2 powders, depending on the content of SiO2 and the treatment temperature (700–1100°C), different crystalline phases (LaCoO3, Co2SiO4 and La9.31(SiO4)6O2) were observed with the crystallite sizes ranging from 50 to 100 nm. It was proved that chemical composition and nature of used additives has influence on the phase formation and structure of obtained nanomaterials