Thermally induced coloration of KBr at high pressures

Abstract

Laser-heated diamond-anvil cell (LHDAC) experiments reveal electronic changes in KBr at pressures between ~13-81 GPa when heated to high temperatures that cause runaway heating to temperatures in excess of ~5000 K. The drastic changes in absorption behavior of KBr are interpreted as rapid formation of high-pressure F-center defects. The defects are localized to the heated region and thus do not change the long-range crystalline order of KBr. The results have significant consequences for temperature measurements in LHDAC experiments and extend the persistence of F-centers in alkali halides to at least 81 GPa.

Evidence for Fe-Si-O liquid immiscibility at deep Earth pressures

“…Care was taken to include only data that did not experience runaway heating that can occur at temperatures near the melting point of KBr (SI Appendix, Fig. S11) (47,48).…”

Measurements of thermal conductivity across the B1-B2 phase transition in NaCl

“…We do not see evidence of thermal runaway at our P, T conditions, as has been reported at higher pressures and temperatures. 25 The thinning of the materials in the cell, including the gasket, sample, and metal foil, can affect the peak temperature measured. Figure 1(d) shows the temperature versus laser power output of a set of heat flow model runs describing a hypothetical sample undergoing pressureinduced changes in geometry and thermal conductivity.…”

Enhancing the electrochemical performance of TiO2 based material using microwave air plasma treatment with an ECR cavity

“…Further, a Tauc equation determines the respective band gap of the untreated and plasma-treated samples, as shown in Figure 3B . From the literature, we found that TiO 2 has a ∼3.2 eV band gap ( Makuła et al, 2018 ), and potassium bromide has a 7.2 band gap value ( Arveson et al, 2018 ). Figure 3B shows that the untreated samples’ band gap lies below 6 eV (∼5.94), which is higher than TiO 2 and below from KBr.…”