Thermal Emission of Alkali Metal Ions from Al 30 -Pillared Montmorillonite Studied by Mass Spectrometric Method

The thermal emission of alkali metal ions from Al -pillared montmorillonite in comparison with its natural form was studied by mass spectrometry in the temperature range 770-930 K. The measurements were carried out on a magnetic mass spectrometer MI-1201. For natural montmorillonite, the densities of the emission currents ( ) decrease in the mass spectrum in the following sequence (T = 805 K, A/cm ): K (4.55 · 10 ), Cs (9.72 · 10 ), Rb (1.13 · 10 ), Na (1.75 · 10 ), Li (3.37 · 10 ). For Al -pillared montmorillonite, thermionic emission undergoes temperature-time changes. In the low-temperature section of the investigated range (770-805 K), the value of increases substantially for all ions in comparison with natural montmorillonite (T = 805 K, A/cm ): Cs (6.47 · 10 ), K (9.44 · 10 ), Na (3.34 · 10 ), Rb (1.77 · 10 ), and Li (4.59 · 10 ). A reversible anomaly is observed in the temperature range 805-832 K: with increasing temperature, the value of of alkaline ions falls abruptly. This effect increases with increasing ionic radius of M . After a long heating-up period, this anomaly disappears and the ln - 1/ dependence acquires a classical linear form. The results are interpreted from the point of view of the dependence of the efficiency of thermionic emission on the phase transformations of pillars.