This paper describes the concept of a new, efficient high-temperature oxygen sorption process based on a perovskite-type ceramic sorbent for oxygen removal and air separation. The new sorption process takes advantage of the unique properties of certain perovskite-type ceramics that can adsorb a large quantity of oxygen, but not other gases, at high temperatures (300-800 °C). The essential principle of this new sorption process is based on the changing of oxygen nonstoichiometry of the perovskite-type ceramics with temperature and oxygen partial pressure. Two highly oxygen-deficient perovskite oxides, La 0.1 Sr 0.9 Co 0.5 Fe 0.5 O 3-δ , and La 0.1 Sr 0.9 Co 0.9 Fe 0.1 O 3-δ , were examined as candidate materials for the oxygen sorption process. Oxygen sorption equilibrium properties were studied by thermogravimetric analysis (TGA) at 500 and 600 °C and oxygen pressures ranging from 1.3 × 10 -4 to 1 atm. The oxygen removal performance at 500 and 600 °C was also investigated in a fixed-bed adsorption column. An infinitely large selectivity, a relatively high oxygen sorption capacity, and fast sorption kinetics are the main characteristics of this new type of sorbent. The process can be used to remove trace oxygen from other gases or to produce high-purity nitrogen and ultrapure oxygen from air.
Excitonic insulators (EIs) arise from the formation of bound electron-hole pairs (excitons) 1, 2 in semiconductors and provide a solid-state platform for quantum many-boson physics 3-8 . Strong exciton-exciton repulsion is expected to stabilize condensed superfluid and crystalline phases by suppressing both density and phase fluctuations 8-11 . Although spectroscopic signatures of EIs have been reported 6, 12-14 , conclusive evidence for strongly correlated EI states has remained elusive. Here, we demonstrate a strongly correlated spatially indirect two-dimensional (2D) EI ground state formed in transition metal dichalcogenide (TMD) semiconductor double layers. An equilibrium interlayer exciton fluid is formed when the bias voltage applied between the two electrically isolated TMD layers, is tuned to a range that populates bound electron-hole pairs, but not free electrons or holes [15][16][17] . Capacitance measurements show that the fluid is exciton-compressible but chargeincompressibledirect thermodynamic evidence of the EI. The fluid is also strongly correlated with a dimensionless exciton coupling constant exceeding 10. We further construct an exciton phase diagram that reveals both the Mott transition and interaction-stabilized quasi-condensation. Our experiment paves the path for realizing the exotic quantum phases of excitons 8 , as well as multi-terminal exciton circuitry for applications 18-20 . 24 . We achieve these properties in atomic 2D semiconductor double layers, whose emergence has opened new paths to realize and control the many-exciton states [15][16][17][23][24][25][26][27][28][29][30][31][32] . Both the formation of dipolar excitons (i.e. excitons with a permanent dipole) and the reduced dielectric screening of the electrostatic interactions favor strong exciton-exciton repulsion. Separate electrical contacts to isolated electron and hole layers provide a reservoir for interlayer excitons with a conveniently tunable chemical potential that allows us to probe thermodynamic properties of the exciton fluid 15,16,24 .
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