Preparation and analysis of chemically gradient functional bioceramic coating formed by pulsed laser deposition P. Rajesh • C. V. Muraleedharan • S. Sureshbabu • Manoj Komath • Harikrishna Varma Received: 5 August 2011 / Accepted: 11 November 2011 / Published online: 22 November 2011 Ó Springer Science+Business Media, LLC 2011 Abstract Bioactive ceramic coatings based on calcium phosphates yield better functionality in the human body for a variety of metallic implant devices including orthopaedic and dental prostheses. In the present study chemically and hence functionally gradient bioceramic coating was obtained by pulsed laser deposition method. Calcium phosphate bioactive ceramic coatings based on hydroxy- apatite (HA) and tricalcium phosphate (TCP) were depos- ited over titanium substrate to produce gradation in physico-chemical characteristics and in vitro dissolution behaviour. Sintered targets of HA and a-TCP were deposited in a multi target laser deposition system. The obtained deposits were characterized by X-ray diffraction, fourier transform infrared spectroscopy, scanning electron microscopy and energy dispersive X-ray analysis. Induc- tively coupled plasma spectroscopy was used to estimate the in vitro dissolution behaviour of coatings. The variation in mechanical property of the gradient layer was evaluated through scratch test and micro-indentation hardness. The bioactivity was examined in vitro with respect to the ability of HA layer to form on the surface as a result of contact with simulated body fluid. It could be inferred that chem- ically gradient functional bioceramic coating can be pro- duced by laser deposition of multiple sintered targets with variable chemical composition. 1 Introduction Titanium and its alloys have been extensively used as load- bearing biomaterial for implantation because of its very favourable biocompatibility with living tissue [1–3]. Tita- nium implants having calcium phosphate coatings, espe- cially hydroxyapatite (HA) on their surface show good fixation to the bone [4, 5]. The use of different techniques to coat metallic implants with calcium phosphate materials is aimed at the combination of the strength properties of the metal with the bioactive character of the ceramic, leading to better bone bonding with the newly remodelled bone and provides better implant functionality [6–9]. The most studied approach has been the application of calcium phosphate coatings by plasma spray and ion sputtering [10– 13]. However, both techniques have failed to produce reliable and long lasting coatings due to weak metal/cera- mic interfaces. Moreover, the high temperature utilized in the plasma spray technique of ceramic such as HA, gives rise to partial decomposition of HA, leading to nonstoi- chiometric phases and inhomogeneous microstructure [14, 15]. The excessive compactness of the coatings manufac- tured by ion sputtering, which hampers the osseointegra- tion, are additional problems associated to these techniques [12, 13]. The pulsed laser deposition (PLD) technique is gathering interest due to its versatility and controllability to produce thin bioceramic coatings as HA, tricalcium phos- phates (TCP) and amorphous calcium phosphate coatings with diverse compositions and crystallinity. Thin coatings produced by PLD are advantageous for high fatigue resistance and adhere well to the metal substrates so that no detachment from the substrates is observed [16–20]. Among the family of biocompatible apatites the most common synthetic bone substitute is HA and others include TCP (alpha and beta) and brushite. HA is the most stable of P. Rajesh  S. Sureshbabu  M. Komath  H. Varma (&) Bioceramics Laboratory, Biomedical Technology Wing, Sree Chitra Tirunal Institute for Medical Sciences and Technology (SCTIMST), Trivandrum 695012, Kerala, India e-mail: varma@sctimst.ac.in; prhkvarma@gmail.com C. V. Muraleedharan Division of Artificial Internal Organs, Biomedical Technology Wing, Sree Chitra Tirunal Institute for Medical Sciences and Technology (SCTIMST), Trivandrum 695012, Kerala, India 123 J Mater Sci: Mater Med (2012) 23:339–348 DOI 10.1007/s10856-011-4501-6