X-ray photoelectron spectroscopy and x-ray excited Auger spectroscopy studies of manganese thiophosphate intercalated with sodium ions.

Polycrystalline powders of Na_2xMn_1-xPS₃ have been synthesized from layered MnPS₃ material by successive ion-exchange intercalation of potassium and sodium ions. Their x-ray photoelectron spectroscopy (XPS) and x-ray excited Auger spectroscopy spectra have been measured at room temperature using Mg Kα (1253.6 eV) x-ray source. In particular, the Mn, P, and S 2p and Na 1s and 2p core-level regions and the Na Auger KL₂₃L₂₃ transition have been investigated. All the analyzed XPS core-level spectra display a single-peak structure, suggesting the absence of nonequivalent atoms of Na, Mn, P, and S. The manganese XPS spectrum shows, as observed in MnPS₃ and in its cesium and potassium intercalation compounds, typical shake-up satellites, suggesting that the Mn–S bond is yet mainly ionic in nature. The comparison with the XPS spectra relative to MnPS₃ and its potassium intercalation compound (K_2xMn_1-xPS₃) does not emphasize any relevant difference in the binding energy positions of the investigated core levels, indicating that sodium ion intercalation process does not alter the electronic properties of pure host matrix. Moreover, Na 2p core levels are discrete and well localized in agreement with the hypothesis of a weak link between the guest (the Na⁺ ions) and the host lattice (the negatively charged Mn_1-xPS₃ sheets). Such a hypothesis finds confirmation by the calculation of the Na modified Auger parameter. [ABSTRACT FROM AUTHOR]