Observation on the effects of rare earth impurities on the properties of Ce0.9Gd0.1O0.195 (GDC) composite electrolyte has been performed. Indonesia has abundant rare earth elements especially CeO2, which one of the resources is from monazite mineral. In this study, the GDC powders were synthesized via solid state technique. The two types of precursors were prepared and mixed into planetary ballmill, i.e., CeO2 (Sigma Aldrich) with Gd2O3 (Sigma Aldrich) and CeO2 (non-commercial, local product) with Gd2O3 (Sigma Aldrich), namely GDC commercial and GDC non-commercial, respectively. The composite electrolyte powders calcined at temperature of 800°C in the air atmosphere condition. The composite electrolytes were then characterized in terms of its morphology, elemental, phase structure and thermal properties of the powders. The GDC commercial and non-commercial powders both consist of face centered cubic fluorite ceria structure which was confirmed by X-Ray Diffraction (XRD). The peaks are matching well with the cerium oxide JCPDS card No: 34-394. There are no peaks detected for the gadolinium oxide. It indicates that the dopant ion is fully substituted into the CeO2 lattice. The elemental analysis was performed using X-ray Fluorescence (XRF). The microstructures were observed under Scanning Electron Microscopy (SEM). The thermal properties characterizations were performed by using Thermal Gravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) from room temperature to 1500°C. Both powders investigated are suitable for electrolyte IT-SOFC based on their physical and thermal characterization. Among the composite electrolytes investigated, the GDC commercial showed the better performance in terms of their physical and thermal properties.

Gadolinium doped cerium (Ce0.9Gd0.1O1.95 or GDC10) was successfully synthesized using the solid-state method. Commercially available CeO2 and Gd2O3 powders were used as starting materials. They were mixed in a ball mill where alumina balls were added as grinding medium with the ratio to powders as of 1:2. The obtained powders were dried and then calcined at temperatures of 600, 700 and 800 °C, respectively. The objective of this research was to investigate the effects of calcination temperature on the properties of GDC10. The powders were characterized using XRF, TGA, XRD, and PSA instruments. XRF analysis shows the presence of Ce, Gd and O elements in stoichiometric composition without any impurities. XRD analysis showed single phase structure of CeO2 where the crystallite size and lattice parameter increases and decreases, respectively, as the calcination temperature increases. The smallest particle size of 647.3 nm was obtained at the calcination temperature of 600 °C. The density of all GDC10 samples sintered at 1350 °C was found to be higher than 95%. In addition, the calcination temperature also influenced the ionic conductivity where the highest obtained value was 0.0153 S.cm-1 at 800 °C for the sample calcinaed at 600 °C. The results suggest that the calcination temperature affected the properties of GDC10 for solid oxide fuel cell application.

The LaNi5 intermetallic phase has been extensively investigated because of its excellent properties, such as attractive hydrogen storage, medium plateau pressure, and easy activation. LaNi5 phase is generally produced by a complicated method, which involves several steps, i.e. melting, alloying, casting, softening and making them into powder. This study aimed to develop a new LaNi5 synthesis process by modifying the combustion-reduction method. In this method it is very important to produce La2NiO4, because LaNi5 is formed from the process of reducing this phase. The precursor powders La(NO3)3.6H2O and Ni(NO3)2.6H2O were reacted with distilled water as a solvent medium and mixed using magnetic stirring. The synthesis process was carried out at room temperature, 60 °C, 70 °C, and 80 °C for 10 minutes until the solution became transparent green. The solution was then dried for 2 hours at 100 °C to form a transparent green gel. The gel was calcined at a temperature of 500 °C for 2 hours, producing a black powder. The optimal black powder was then reduced using CO gas at 600 °C for 2 hours. The powder samples were characterized using XRD, FTIR, and SEM-EDX. The analysis revealed that synthesis at room temperature was the most optimal method for the reduction process because it produced the most La2NiO4, at 12.135 wt%.

Lithium-ion battery has been drawing attention from researchers due to its excellent properties in terms of electrochemical and structural stability, low cost, and high safety feature, leading to prospective applications in electric vehicles and other large-scale applications. However, lithium-ion batteries are still in charging time owing to its low conductivity, restricting its wide applications in large-scale applications. In this work, therefore, lithium lanthanum titanate (LLTO) was synthesized derived from lanthanum oxalate, as a lanthanum source, for an anode active material application in the lithium-ion batteries due its high electrochemical conductivity and pseudocapacitive characteristics. To the best our knowledge, our work is the first one to synthesize LLTO from lanthanum oxalate as the lanthanum source. Commercial lithium carbonate and commercial titanium oxide were used as the lithium and titanium sources, respectively. It was used low cost and simple solid-state reaction process to synthesize this material and performed a two-step calcination processs at 800 oC for 8 hours and 1050 oC for 12 hours under ambient atmosphere. The physical characteristics showed that LLTO possesses high purity (98.141%) and micro sized grains with abundant empty spaces between the grains. This, therefore, lead to improve electrochemical performances such as stable discharge capacity at low potential even near to zero (98.67 mAh), and a high conductivity of 2.45 × 10-2 S/cm at room temperature. This LLTO is interesting to be used as the anode active material in low potential lithium-ion battery applications.

Elektrolit berbasis serium seperti GDC10 telah banyak dikembangkan untuk aplikasi sel bahan bakar oksida padatan suhu sedang atau yang dikenal dengan Intermediate Temperature Solid Oxide Fuel Cell (IT-SOFC). Kodoping merupakan salah satu cara untuk meningkatkan konduktivitas elektrolit IT-SOFC. Tujuan dari penelitian ini adalah untuk mempelajari pengaruh penambahan kodopan neodimium (Nd) terhadap GDC10 (Ce0,9Gd0,1-xNdxO1,90) dengan rasio molar x = 0,025; 0,050; dan 0,075 terhadap sifat fisis dan elektrokimianya. Neodimium digunakan sebagai kodopan karena dapat menurunkan energi aktivasi, sehingga konduktivitas elektrolit meningkat. Metode sintesis yang digunakan adalah sol gel untuk menghasilkan serbuk GDC terdoping Nd, setelah itu serbuk dibuat pelet. Sampel dikarakterisasi dengan menggunakan X-Ray Diffraction (XRD) untuk mengidentifikasi fasa, Scanning Electron Microscope (SEM) untuk melihat morfologi dan Thermal Gravimetric Analysis (TGA) untuk melihat stabilitas termalnya. Dari hasil penelitian, kalsinasi pada suhu 700 oC selama 5 jam dan sintering pada suhu 1350 oC selama 2 jam diperoleh densitas pelet elektrolit lebih besar dari 95%. Hal ini telah memenuhi syarat sebagai elektrolit sel bahan bakar padatan yang baik. Keseluruhan sampel memiliki struktur kubik dengan ukuran kristal antara 4,26 nm hingga 4,47 nm. GDC10 terdoping neodimium dengan rasio molar x = 0,025 (GDC-Nd0,025) memiliki konduktivitas tertinggi yaitu 0,055 S/cmpada suhu 600 oC. Hasil tersebut menunjukkan bahwa kodoping dapat meningkatkan konduktivitas sel elektrolit GDC untuk aplikasi sel bahan bakar oksida padatan suhu sedang.

No abstract

Cerium oxide base materials have been attracting great attention as a promising electrolyte for intermediate temperature of solid oxide fuel cell (IT-SOFC) due to its excellent conductivity at a lower temperature. In this works, cerium from Indonesia local raw material was developed as a cheaper alternative precursor for preparing gadolinium doped cerium (Ce0.9Gd0.1O1.95 or GDC10) electrolyte. The effects of polyethylene glycol 400 (PEG 400) as a surfactant on to physical properties of GDC10 electrolyte were studied. GDC10 powders were synthesized using co-precipitation method with the addition of various PEG 400 concentration i.e 0,1,2 and 3v/v%. Synthesized powders were characterized by using X-Ray Diffraction (XRD), Particle Size Analyzer (PSA), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and Fourier Transform Infrared (FTIR) Spectroscopy. The XRD analysis indicates that crystallinity was enhanced and all of the peaks on samples correspond to the fluorite crystal structure of single phase CeO2. The average crystallite size is about 11.37, 7.27, 6.75 and 7.02 nm for PEG 400 concentration of 0, 1, 2 and 3v/v%, respectively. SEM images show different morphology of particle regarding with the addition of surfactant. Particle size analysis exhibits decreasing of particle diameter as the addition of PEG surfactant. The smallest particle size was about 1.47 μm for 1v/v% of PEG concentration. The results of this works confirm that the addition of PEG 400 surfactant strongly affects particle size and morphology of GDC10 powders. However, addition PEG 400 as surfactant should be delivered in a certain amount to give optimum effects where according to this works it is about 1 -2v/v%.

Gadolinium doped cerium (GDC10) banyak dikembangkan sebagai elektrolit ITSOFC. Bahan baku GDC10 diperkirakan dapat memanfaatkan sumber daya alam lokal. Penelitian ini mempelajari sintesis GDC10 menggunakan prekursor Ce(OH)4 (Produk Lokal, 85% Ce) dan Gd2O3 (Produk Lokal, 1,26% Gd) dengan metode kopresipitasi. Tiga jenis senyawa karbonat, yaitu amonium karbonat ((NH4)2CO3), potasium karbonat (K2CO3), dan sodium hidrogen karbonat (NaHCO3), digunakan sebagai agen presipitasi. Serbuk hasil sintesis dikarakterisasi dengan menggunakan X-Ray Diffraction (XRD) dan  Fourier Transform Infrared (FTIR). Penambahan berbagai senyawa karbonat sebagai agen presipitasi dengan prekursor berupa gadolinium dan serium lokal dapat menghasilkan serbuk elektrolit GDC10 dengan struktur kristal  fluorite kubik. Potasium karbonat memiliki kualitas dan performa yang lebih baik sebagai agen presipitasi untuk menghasilkan serbuk elektrolit GDC10 karena menghasilkan ukuran kristalit yang paling kecil sebesar 0,014 nm dibandingkan jenis GDC10 dengan agen presipitasi lainnya. Namun, masih perlu optimasi pada temperatur kalsinasi untuk menghilangkan pengotor berupa karbonat.