Role of Nitrogen Pressure on the Structural and Mechanical Properties of ZrON Composite Films Deposited by Plasma Focus Device

Polycrystalline zirconium oxy-nitride (P-ZrON) composite films are deposited on Zr substrates by plasma focus device. The focusing efficiency of plasma focus is maximum at 1.5 mbar nitrogen pressure (NP) due to more intense signal of high voltage probe. The P-ZrON composite films are deposited for 25 focus shots at different NP. The XRD patterns confirm the evolution of ZrN (111), Zr3N4 (230), Zr3N4 (320), Zr3N4 (140), Zr3N4 (340) and ZrO2 (200) diffraction planes. The peak intensity of different diffraction planes and their broadening are associated with increasing NP. The (N + O)/Zr atomic ratio’s are found to be 0.78, 0.88, 1.31, 0.66 and 0.55 at 0.5, 1.0, 1.5, 2.0 and 2.5 mbar NP respectively. The variation in crystallite size of different planes and strain transformation observed in various planes are attributed to varying ion energy fluxes which are associated with the increase of NP. The lattice parameter of ZrN is found to be 0.461 nm at 0.5 mbar NP which is decreased to 0.457 nm at 1.5 mbar NP. The weight fractions of ZrN, Zr3N4 and ZrO2 phases deposited at 2.5, 2 and 1.5 mbar NP are found to 30.5, 28.5 and 41 % respectively. The SEM microstructures reveal that the size and shape of nano-particles and the formation of complicated network of nano-wires (diameter = ~ 55 nm) and nano-combs are associated with increasing NP. The AFM images show the maximum rms surface roughness of P-ZrON composite film when deposited at 1.5 mbar NP. The micro-hardness (8623 ± 0.95 MPa) of P-ZrON composite film deposited at 1.5 mbar NP is found to be four times the micro-hardness of virgin Zr.