Authors:
Sucharita Sinha
Laser and Plasma Technology Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India

T. R. G. Kutty
Radiometallurgy Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India

P. V. A. Padmanabhan
Laser and Plasma Technology Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India

K. G. K. Warrier
Regional Research Laboratories, Thiruvananthapuram, 6954019 Kerala, India

Pulsed laser deposition (PLD) technique has been successfully employed to generate thin film coating of lanthanum phosphate on various substrates. Sintered targets of lanthanum phosphate were ablated using pulsed Nd:YAG laser radiation. Although, coatings generated by PLD on polished stainless steel substrates, as well as on optically polished quartz samples were found to be uniform and having good homogeneity, the coatings had poor adhesion characteristics with the substrate surface. However, PLD based coating on surface treated stainless steel substrates (either sandblasted or having a pre-coating of NiCrAlY alloy) showed strong bonding with the substrate surface. Structural investigation of the deposited films under scanning electron microscope revealed high level of homogeneity and absence of porosity. PLD based thin film coatings of lanthanum phosphate were observed to be superior in terms of their microstructural characteristics in comparison to plasma based coatings that had a distinctly higher level of residual porosity. Our results suggest that a combination of a thick plasma based coating followed by a PLD based thin overcoat, both of lanthanum phosphates, would result in an effective protective coating that is dense enough to accomplish the function of isolating the substrate from a corrosive environment. Such coatings when deposited on the inside of crucibles would facilitate containment of liquid uranium and other such corrosive liquids.