Chemical synthesis of nanocrystalline CuAlO2 via nitrate-citrate combustion route

The nanocrystalline delafossite CuAlO2 powder was synthesised by a sol-gel nitrate-citrate self-combustion route. Citric acid was introduced both as the chelating and reducing agent or fuel. The citric acid/metal ion ratio was adjusted to provide fuel-lean, stoichiometric or fuel-rich conditions of the redox reaction. Equimolar amounts of copper and aluminium nitrates and the citric acid were dissolved in deionized water. The sol was dried at 80 oC to obtain the gel. By increasing the temperature above 250 oC, the gel immediately ignited, forming the precursor powder. According to the X-ray diffraction analysis the phase pure delafossite was obtained only when the precursor powder was prepared from the stoichiometric redox reaction, and after the calcination for 4 h in Ar atmosphere at 920 oC. The field emission scanning electron micrographs revealed the cauliflower aspect of the calcined powder, where small primary particles formed the agglomerates. The formation of the phase pure CuAlO2 powder was also confirmed by Fourier transformed infrared spectroscopy

Subsolidus phase equilibria in the RuO2 - Bi2O3 - SiO2 system

Subsolidus equilibria in the RuO2–Bi2O3–SiO2 diagram were studied with the aim of investigating possible interactions between the bismuth-ruthenate- based conductive phase and the silica-rich glasses in thick-film resistors. The tie lines are between Bi2Ru2O7 and Bi12SiO20 (gamma phase), between Bi2Ru2O7 and Bi4Si3O12, and between RuO2 and Bi4Si3O12. This indicates that the bismuth ruthenate is not stable in the presence of the silica-rich glass phase

Bulk relaxor ferroelectric ceramics as a working body for an electrocaloric cooling device

The electrocaloric effect (ECE), i.e., the conversion of the electric into the thermal energy has recently become of great importance for development of a new generation of cooling technologies. Here, we explore utilization of [Pb(Mg1/3Nb2/3)O3]0.9[PbTiO3]0.1 (PMN-10PT) relaxor ceramics as active elements of the heat regenerator in an ECE cooling device. We show that the PMN-10PT relaxor ceramic exhibits a relatively large electrocaloric change of temperature TEC >1 K at room temperature. The experimental testing of the cooling device demonstrates the efficient regeneration and establishment of the temperature span between the hot and the cold sides of the regenerator, exceeding several times the TEC within a single PMN-10PT ceramic plate