Diagnostics of a Radio-Frequency Plasma Expanding Through a Nozzle (PETN) at Low Pressure

The diagnostics of the radio-frequency (induction mode) plasma expanded through a nozzle (PETN) at low pressures (100–1000 Pa) was performed by on-line optical emission spectroscopy (OES) and on line quadrupole mass spectrometry (QMS). The OES was used for evaluating the electronic, vibrational, and rotational temperatures (T_e, T_v, and T_r) along the plasma reactor before and after the nozzle. The PETN gas mixtures analyzed were Ar+N₂, Ar+CO, and Ar+O₂with an addition of 1 vol.% N₂to the last two gas mixtures. For the same conditions in the PETN the values of T_e, T_v, and T_r were found to be different for the different gas mixtures and related to the depopulation of excited N₂⁺ by oxygen atoms. Moreover the Ar+O₂PETN aqueous solutions of lanthanum and manganese nitrates were nebulized for the deposition of LaMnO₃perovskite. The QMS, in real time, measuring the mass species formed before and after the nozzle, explained the reasons in the different values of T_e, T_v, and T_r for the three gas mixtures as well as for the formation of oxides in the PETN from the aqueous nitrate solutions.