Processing effects on in-flight particle state and functional coating properties of plasma-sprayed manganese zinc ferrite

Magnetic properties of manganese zinc ferrite (MZF) coatings deposited by atmospheric dc plasma spraying largely depend on zinc and oxygen loss during particle flight. The temperature and velocity of in-flight MZF particles were widely varied by changing plasma spray conditions to examine these chemistry changes and resultant magnetic properties. Zn loss increases with increased particle temperature or decreased particle velocity. Meanwhile, wüstite (FeO) formation, related to the oxygen loss, is more complicated, partly because oxygen, which is lost during flight in the high-temperature zone of the plasma jet, can be recovered at longer spray distances. As a result, the saturation magnetization of MZF coatings decreases and the coercivity increases with increased particle temperature or decreased particle velocity.