Production of barium ferrite films using an inductively coupled plasma reactor

The production of barium ferrite films has being studied using Plasma Assisted Chemical Vapor Deposition in an Inductively Coupled Plasma (ICP) Reactor. Solutions containing dissolved salts of iron and barium were used as precursors. The solution is atomized in the hot region of the plasma, then the gases impinge on a substrate holder. A new rotating substrate was designed and built to control the kinetics of film deposition and to ensure the uniformity of the deposited layers. Vycor glass #7913 was used as the substrate material due to its properties and relatively low cost. Pure argon and combinations of argon and oxygen were used as plasma gases. The power of the plasma torch was varied as well as the rotational speed and the distance of the substrate from the plasma torch exit. The molar ratio of iron to barium in the feed solution was also varied. A thermochemical analysis of the Ba - Fe - O system was performed to predict the conditions for the formation of barium hexaferrite. Deposited films were characterized using Scanning and Transmission Electron Microscopy, Vibrating Sample Magnetometry and X-Ray Diffraction. It was shown that it is possible to grow films of crystalline barium hexaferrite on Vycor glass without any pre or post-treatment at temperatures above 800°C. Films that were amorphous after deposition were heat treated in an oxygen atmosphere to crystallize the barium hexaferrite. A Mathematical model that describes the heat and mass transfer in the reactor was presented. It was expected that using a near atmospheric pressure ICP would demonstrate technological and economical advantages over existing methods.