Rapid preparation of [Ca23.04Sr0.96Al28O64]4+(4e−) electrides block by spark plasma sintering

Abstract

In this paper, the Ca11.52Sr0.48Al14O33 +Ca2.88Sr0.12Al2O6 of a specific stoichiometric ratio is used as a precursor. The [Ca23.04Sr0.96Al28O64]4+(4e-) electrides block with a high electron concentration successfully prepared by in-situ aluminothermic reaction using a spark plasma sintering system(SPS). The sintering temperature is 1050 °C, and the holding time is 5 min. The UV spectrophotometer results showed that (Ca0.96Sr0.04)12A7:e- showed the visible UV absorption peak at around 2.5 eV, and the electron concentration was calculated to reach 2.2 × 1021 cm−3. Simultaneously, the electronic structure is analyzed by a paramagnetic resonance spectrometer, and the result shows that electrons are injected uniformly in the sample. The synchronous thermal analyzer's results showed that (Ca0.96Sr0.04)12A7:e- weight loss occurred above 700 °C was derived from oxygen desorption. These results altogether demonstrate that electrons are efficiently injected into the cage structure of (Ca0.96Sr0.04)12A7:e-. This process provides a new electron-injection method, which significantly shortens the preparation cycle of (Ca0.96Sr0.04)12A7:e- and makes mass production of samples possible. The electronic structure of (Ca0.96Sr0.04)12A7:e- calculated using first-principles. The results show a cage conduction band (CCB) between − 1 eV and 0.7 eV, which is favorable for electrical performance. The results also show that the excellent electrical transport performance of (Ca0.96Sr0.04)12A7:e- mainly comes from Sr, Ca atom s-state electrons, and Al atom p-state electrons.