We review the mechanism of spin-lattice coupling in relieving the geometrical frustration of pyrochlore antiferromagnets, in particular spinel oxides. The tetrahedral unit, which is the building block of the pyrochlore lattice, undergoes a spin-driven Jahn-Teller instability when lattice degrees of freedom are coupled to the antiferromagnetism. By restricting our considerations to distortions w...

A wide range (y = 0.05—0.33) of Co-doped LiCo5Mn2_504 spinels were synthesized and electrochemically characterized. These Co-doped spinels showed improved specific capacity and capacity retention over pure spinels. Electrochemical impedance spectroscopy and the linear polarization resistance technique were used to determine the transport and electrochemical kinetic parameters of Co-doped spinel...

Many compounds with the spinel structure type have been analyzed for their thermoelectric properties. Published data was used to augment experimental results presented here to select promising thermoelectric spinels. Compounds studied here include C~~,~Al~.5Cr2Se4, Cu05Coo.5Cr2Se4, C~o,~Ino,~Cr2Se~ and CuIr2Se4. Many exhibit low lattice thermal conductivity of about 20 mW/cmK, independent of te...

In this study, 38CrMoAl steel was treated with calcium under the pressure of 2 MPa, and four groups high aluminum steels highest content 0.01% were obtained. Spinel inclusions MgO content, CaO original spinel morphology found by testing analyzing towards composition in Ca steel. Combined thermodynamic calculation, a Ca–Al reaction model proposed, solid/liquid phase denaturation mechanism explor...

Abstract Compact type A calcium‐aluminum‐rich inclusions (CTA CAIs) are believed to have experienced partial melting that erased all information on their original nebular condensation. To investigate this question, we report new microstructural data a CTA CAI, composed primarily of melilite, spinel, and perovskite, in the Northwest Africa 5028 CR2 chondrite. The melilite grains contain low (5–1...

This contribution deals with new geology, petrography, and bulk-rock/mineral chemistry of the poorly studied ultramafics Wadi Ibib–Wadi Shani (WI–WS) district, South Eastern Desert, Egypt. These are dismembered ophiolitic rocks that can be subdivided into serpentinites serpentinized peridotites. Primary minerals such as olivine pyroxene absent in serpentinites, but relics them occur Pseudomorph...

Fine-grained, spinel-rich inclusions (FGIs) are abundant in CV3 chondrites and exhibit textures compositions that consistent with a condensation origin. We have conducted systematic investigation of FGIs from two reduced chondrites, Leoville Efremovka, which has revealed number microscale variations the primary mineralogies nodules, provided further insights into origins FGIs. Nodules individua...

Precipitation of large crystals/agglomerates of spinel and their accumulation in the pour spout riser of a Joule-heated ceramic melter during idling can plug the melter and prevent pouring of molten glass into canisters. Thus, there is a need to understand the effects of spinel-forming components, temperature, and time on the growth of crystals in connection with an accumulation rate. In our st...