Figure 6.

Time-temperature dependence of sodium and potassium vapor pressures over KNN, previously prepared by the calcination of the stoichiometric oxide-carbonate mixture at 950 °C for 12 h. Note that the analysis was performed in vacuum, so the results cannot be directly correlated with heating experiments performed in air, where the evaporation rates of the alkalis are much lower. (Reprinted with permission from [86]. Copyright 2015 The Royal Society of Chemistry).