G Processing and characterization of CaTiO 3 perovskite ceramics
Calcium titanate (CaTiO3) ceramics with perovskite structure were produced by solid state reaction. Calcium carbonate (CaCO3) and titanium dioxide (TiO2) were mixed (in molar ratios 1/1 and 3/2), and the obtained mixtures were calcined at 1150 °C in successive thermal cycles. The obtained samples were characterized by differential thermal analysis, thermogravimetry, X-ray diffraction, measurement of particle size distribution and linear thermal shrinkage. XRD results indicated that the samples have perovskite CaTiO3 structure with small amount of secondary CaO and TiO2 phases, and their phase composition depends on the heat treatment conditions. The measured values of electrical resistivity were within the characteristic range of insulating materials and approach values corresponding to semiconducting ceramics.
Synthesis and Characterization of Ca-doped Li4Ti5O12 Using CaCO3 from Chicken Eggshell as a Dopant for Lithium-Ion Battery Anode Material
In order to improve the performance of Li4Ti5O12 (LTO) anode, this research was focused on Ca2+ion doping as a substitute to Li+ ion to form Li4-xCaxTi5O12with values of x=0, 0.05, 0.075, and 0.125 using solid-state reaction. The Ca2+ion source was CaCO3which synthesized from the chicken eggshell. The LTO was prepared by a solid-state method using TiO2 Degussa. The pristine LTO and Ca-doped LTO sample powder was characterized by XRD, SEM, and were also tested its electrochemical performance by EIS, CV and CD. The CaCO3 dopant characterization results showed CaCO3 in calcite polymorph as the main phase, with agglomerated fine particulate morphology and high purity. Characterization of LTO sample powder with XRD revealed that dopant Ca successfully enter the structure of LTO spinel, with maximum addition level x=0.05, which excessive addition led to CaTiO3 impurity forming. SEM result showed all Ca-doped LTO have almost similar morphology, which was agglomerated particulate. Ca-doped LTO samples have smaller particle size compared to pristine LTO. Electronic conductivity improvement was spotted at all of Ca-doped LTO sample, with Li3.75Ca0.125Ti5O12 (LCaTO-3) showed the lowest charge transfer resistance of 29.5 Ω. Li3.75Ca0.125Ti5O12(LCaTO-3) also had the highest initial discharge capacity of 168.2 mAh/g. Nevertheless, in high rate application, the best performance was showed by Li3.85Ca0.075Ti5O12(LCaTO-2) with the discharge capacity of 30.2 mAh/g at 12 C, which capacity retention percentage of 21.43% compared to its discharge capacity at 0.2 C.
Titanate Nanofiber Reactivity: Fabrication of MTiO3 (M = Ca, Sr, and Ba) Perovskite Oxides
Titanate nanofiber, as an important morphology of one-dimensional nanostructured titanate, not only can be regarded as the final product derived from alkaline-hydrothermal treatment of bulk TiO2 but also can serve as initial reactant for fabricating complex functional materials with their parent morphology, which may be difficult to achieve using their bulk material counterparts under mild hydrothermal conditions. Based on titanate nanofiber reactivity, ternary MTiO3 (M = Ca, Sr, and Ba) perovskite oxides with specific morphologies have been fabricated in alkaline solution at low temperature via a soft chemical route. The resulting CaTiO3 products possessed a microtubular structure with rectangular cross-section, while SrTiO3 and BaTiO3 showed the assemblies consisting of aggregated particles in a compact fashion. On the basis of the experimental results, we have proposed two types of growth mechanisms to elucidate the formation processes of CaTiO3, SrTiO3, and BaTiO3 microstructures, respectively. The fa...