Effect of Sm3+ Substitutions on the Lithium Ionic Conduction and Relaxation Dynamics of Li5+2xLa3Nb2−xSmxO12 Ceramics

In the present work, we studied the effects of substitutional Sm3+ ions on the ionic conduction properties of Li5+2xLa3Nb2−xSmxO12 (LLN-Sm) ceramics with x = 0.0—0.6. The investigated final ceramics, prepared by solid state reaction, were sintered at 1000 °C for 12 h. XRD investigations showed the formation of the cubic garnet phase for all of the studied samples. The ionic conductivity was found to increase with Sm3+ content, with the highest value of 7.04 × 10−5 S/cm for the Li5+2xLa3Nb2−xSmxO12 sample compared to 7.49 × 10−6 S/cm for the pure LLN sample, both at RT. Lithium ion mobilities of LLN-Sm garnets at different temperatures were estimated. Considerable enhancement of mobility, the main factor leading to ionic conductivity improvement, was obtained for samples with Sm3+ substitutions. Relaxation processes were studied by the electric modulus, and the corresponding activation energy was found to be very similar to the ionic conduction process.

Preparation and Characterization of Sol–Gel-Driven LixLa3Zr2O12 Solid Electrolytes and LiCoO2 Cathodes for All-Solid-State Lithium-Ion Batteries

In the current study, we prepared a LixLa3Zr2O12 ((Al, Ta) LLZO) powder doped with 0.2 mol of Al and Ta using the sol-gel method and subsequently used it to fabricate solid electrolyte pellets. In pellets with lithium content of 6.2 and 6.82 mol, a cubic phase and a lithium-deficient pyrochlore mixed-phase were respectively observed. However, when the lithium content was 8.06 mol, a lithium-excess phase was also observed. Meanwhile, at 7.44 mol lithium, the (Al, Ta) LLZO ceramic pellets showed a pure cubic garnet phase with no secondary phase. When lithium was added excessively, a non-granular morphology was observed at the (Al, Ta) LLZO fracture surface in which the grains were tightly bonded by the liquid phase formed during sintering. Nyquist plots of the pellets showed that the effect of grain boundaries was eliminated and the pellets exhibited a high lithium ion conductivity of 4.26 × 10−4 S/cm. Using spin coating and multi-step heat treatment, we deposited LiCoO2 (LCO) thin films on (Al, Ta) LLZO pellets to form cathodes. There was no significant interdiffusion between the LCO cathode and (Al, Ta) LLZO solid electrolyte and morphological analysis indicted that a thin interfacial layer (~10 nm) was formed between the LCO and the electrolyte. Finally, we demonstrated an all-solid-state rechargeable battery in the form of a coin cell comprising of an LCO cathode, Li metal anode, and (Al, Ta) LLZO solid electrolyte, which could yield a discharge capacity of ~100 mAh/g.

X-Ray Diffraction Analysis of YSAG:Yb Ceramic Powders with Different Stoichiometry

Synthesis of YSAG:Yb ceramic powders with different stoichiometry by chemical precipitation method was carried out. It has been established that scandium can replace both dodecahedral and octahedral positions of garnet. It is shown that scandium is embedded in those positions that become available to it when the YAG:Yb composition deviates from stoichiometric. Thus, scandium can compensate for the lack of one of the components of the oxide composition Y2O3, Yb2O3, and Al2O3 during the formation of the garnet phase.

PETROLOGY AND PETROGENESIS OF SIAH KOOH VOLCANIC ROCKS IN THE EASTERN ALBORZ

Siah Kooh area is northeast of Shahroud city and is located in eastern Alborz. The lithologic composition of the volcanic rocks in the area consists of andesite, basalt, trachyandesite and quartztrachite. Plagioclase, olivine, and augite phenocrysts as the main minerals and apatite and magnetite, sericite, chlorite and apacite minerals are sub-minerals of volcanic rocks that are located in the glass slabs. Quartz is also found in fine-grained rock pulp and sometimes in phenocrysts. The dominant texture in these rocks are porphyritic, amygdaloidal and microlithic. According to geochemical studies of basaltic magmatic volcanic rocks, calc-alkaline potassium is high and negative Nb anomaly, Ce / Pb ratio and enrichment of rocks of light rare earth elements (LRRE) and high LREE / HREE ratio indicate contamination. The crust is an indicator of the presence of the garnet phase in the mantle source. On the other hand, the similarity of their trace elements to Oceanic Basalts (OIB) is a clear evidence of their relevance to this environment. Early basaltic magma originated from a mantle with a garnet-lherzolite composition with a partial melting rate of 15–12%. FeOtotal values in basalts and other structural evidence indicate the formation of these rocks in the early stages of intra-continental rifting which can be attributed to the pressure drop caused by intra-continental tidal phases associated with deep faults during the orogenic phases. Alpine attributed to Eocene time.

Deposition of Lu-Fe-O thin films on silica glass substrates by MOCVD

Thin films of the Lu-Fe-O system were deposited by aerosol assisted MOCVD on silica glass substrates. Hexagonal h-LuFeO3, garnet Lu3Fe5O12, perovskite o-LuFeO3 or hematite Fe2O3 phases were obtained, depending on the thermodynamic deposition conditions or post annealing temperature. Magnetic measurements confirm the ferromagnetic behaviour at room temperature of the thin films with garnet phase. An indirect bandgap of 1.78 eV was measured.

Tolerance factor and phase stability of the garnet structure

We introduce a structural descriptor, the tolerance factor, for the prediction and systematic description of the phase stability with the garnet structure. Like the tolerance factor widely adopted for the perovskite structure, it is a compositional parameter derived from the geometrical relationship between multi-type polyhedra in the garnet structure, and the calculation only needs the information of the ionic radius. A survey of the tolerance factor over 130 garnet-type compounds reveals that the data points are scattered in a narrow range. The tolerance factor is helpful in understanding the crystal chemistry of some garnet-type compounds and could serve as a guide for predicting the stability of the garnet phase. The correlation between the tolerance factor and the garnet-phase stability could be utilized by machine learning or high-throughput screening methods in material design and discovery.

High-alumina pyroxenite xenoliths from Quaternary basalts of NW Spitsbergen - evidence of continental crust delamination

The origin of spinel-garnet pyroxenite from xenoliths in Quaternary basaltoids of Spitsbergen Island (Svalbard Archipelago) is discussed. The rocks have a high concentration of Al2O3 and MgO and low Cr. The primary magmatic association Spl-Opx-Cpx and the high Al content in pyroxenes provide evidence for the formation of these rocks as cumulates of hydrous basaltic melts in the lower crust at a pressure of ~1.2 GPa. Transformation of the texture from the magmatic hypidiomorphic to the metamorphic granoblastic and growth of garnet at the expense of spinel and high-alumina pyroxenes indicate transport of rocks to a depth below the spinel/garnet phase transition boundary in the Cr2O3-free CaO-MgO-Al2O3-SiO2 system. The parameters of the Grt-Opx equilibrium range within 1060-1120 °C and 2.2-2.6 GPa. Thus, magmatic pyroxenite was transported to a great depth into the mantle, which provides evidence for delamination in the region of the lower continental crust containing ultramafic cumulates.