Characterization and thermal decomposition of Mg2KH(AsO4)2·15H2O

Abstract

In this work, we present first data on the infrared and Raman spectroscopic characteristics, thermal analysis and solid-state transformations of Mg2KH(AsO4)2·15H2O, which is a unique example of an acid salt containing dimeric units [H(AsO4)2] in its crystal structure. The infrared and Raman spectra recorded at ambient conditions have been studied, and an assignment of the observed vibrational bands has been proposed considering the crystal structure data. The thermal behavior of Mg2KH(AsO4)2·15H2O has been investigated by simultaneous TG/DTA/mass spectrometry experiments in the temperature range up to 1000 °C at different heating rates, and new data on the thermal stability and thermal dehydration of Mg2KH(AsO4)2·15H2O have been obtained. The phase composition after the dehydration processes in the temperature interval of 300–650 °C has been studied by combination of powder XRD and IR spectroscopic analyses. The spectroscopic and thermal properties of Mg2KH(AsO4)2·15H2O have been compared to those of the isostructural phosphate salt Mg2KH(PO4)2·15H2O.