Sucrose‐nitrate auto combustion synthesis of Ce _0.85 Ln _0.10 Sr _0.05 O _{2‐ δ} (Ln = La and Gd) electrolytes for solid oxide fuel cells

Abstract

Summary Nanocrystalline powders of co‐doped ceria oxides Ce0.85La0.10Sr0.05O2‐δ (CLSO) and Ce0.85Gda0.10Sr0.05O2‐δ (CGSO) have been synthesized by auto combustion method at 100°C using sucrose as fuel. Thermal analysis (TGA/DSC) of as‐prepared powders indicated calcination above 400°C to remove organic residue. The average grain size of the pellets sintered at 1200°C for 4 hours is 436 and 683 nm for CLSO and CGSO, respectively. The electrical conductivity of the sintered samples was determined by impedance measurements in the temperature range 300°C to 600°C and the frequency range 20 Hz to 2 MHz. At 600°C, the total electrical conductivity (σt) of CGSO is 6.78 × 10−3 S cm−1, 2.5 times higher than 2.72 × 10−3 S cm−1 of CLSO. Further, it is found that the value of grain boundaries blocking factor (αgb) of CGSO is 0.47 which is 30% lesser than 0.68 of CLSO at 600°C. The higher value of electrical conductivity of CGSO as compared to CLSO is attributed to the lesser blocking effect of grain boundaries, smaller lattice distortion and denser microstructure of CGSO as compared to CLSO. The electrical conductivity of synthesized samples has been compared with the electrical conductivity of similar compositions of co‐doped CeO2 oxides. Our study indicated that the sintering temperature, and hence, the morphology of sintered samples has a significant role in determining the electrical conductivity. The presence of oxygen vacancies in the synthesized samples is experimentally supported by using UV‐visible spectroscopy, Raman spectroscopy, and thermal analysis techniques.

A comprehensive study of dielectric, modulus, impedance, and conductivity of SrCeO3 synthesized by the combustion method

“…The exothermic peak of the DSC curve is a signature of burning of carbon which can be possible due to the presence of unburnt or excess sucrose. 30 Stage III (790 • C−950 • C) exhibits a weight loss of 10.39% which can be attributed to the decomposition of SrCO 3 to SrO. In the DSC curve of as-prepared powder, two endothermic peaks corresponding to weight loss stages I and III are also seen.…”

“…We have further noticed that the value of DC conductivity (1.2 × 10 −3 Ω −1 cm −1 at 600 • C) and activation energy .79 eV is very close to the values reported for doped CeO 2 -based oxide ion conductors for SOFCs. 30 Values of the activation energy obtained for the relaxation and conduction mechanism of grain and grain boundaries are summarized in Table 4. From Table 4, it is noticed that the activation energy for total DC conductivity is lower than that for grain boundary conduction but higher than that for grain conduction.…”

“…Tunable blue-yellow and orange-red emissions from SrCeO 3 doped with samarium and dysprosium have been reported. 26 In the literature synthesis of SrCeO 3 by different methods such as co-precipitation, 27 spray pyrolysis, 28 spin coating, 29 combustion synthesis, 30 solid-state reaction, 31 sol-gel, 32 have been reported. Researchers have used fuels such as citric acid, urea, glycine, and others for the synthesis of SrCeO 3 through the combustion method.…”

“…Using sucrose as fuel, doped CeO 2 oxide ion conductors have been synthesized successfully at room temperature. 30 The objective of this work is to synthesize SrCeO 3 powder through the combustion method using sucrose as fuel. Phase evolution with the help of Xray diffraction (XRD) has been studied minutely by the heat treatment of the prepared sample at various temperatures.…”

Thermally activated polaron tunnelling conduction mechanism in Sr2MnO4 synthesized by quenching in ambient atmosphere

“…The spectrum shows a sharp absorption edge close to the bandgap. To determine the band-gap, absorption data has been plotted according to the Tauc's equation for direct bandgap, given by [17]:…”