Biomaterials 24 (2003) 5131–5137 Effect of post-deposition heating temperature and the presence of water vapor during heat treatment on crystallinity of calcium phosphate coatings Yunzhi Yang a , Kyo-Han Kim a,b , C. Mauli Agrawal c,d , Joo L. Ong a,d, * a Health Science Center at San Antonio, Department of Restorative Dentistry, Division of Biomaterials, The University of Texas, MSC 7890, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA b Department of Dental Biomaterials, College of Dentistry and Institute of Biomaterials Research and Development, Kyungpook National University, 2-101 Dongin Dong, Jung-Gu, Daegu 700-422, South Korea c College of Engineering, The University of Texas at San Antonio, 6900 N. Loop 1604, San Antonio, TX 78249-0619, USA d Health Science Center at San Antonio, Center for Clinical Bioengineering, The University of Texas, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA Received 29 January 2003; accepted 15 June 2003 Abstract In this study, radiofrequency sputtered calcium phosphate (CaP) coatings were evaluated after 1 h post-deposition heat treatment at either 350  C, 400  C, 450  C, 500  C or 600  C in the presence or absence of water vapor. X-ray diffraction analyses indicated the as-sputtered coatings to be amorphous. With different post-deposition heat treatments used, in this study, crystallinity of CaP coatings was observed to be in the range of 0–68%. The 400  C and 450  C heat-treated CaP coatings in the absence of water vapor were poorly crystalline, exhibiting a crystallinity of 271%. In comparison to heat treatments at 450  C in the absence of water vapor, the presence of water vapor at 450  C heat treatment resulted in a significant increase in coating crystallinity. However, this effect was not observed at higher temperatures. A coating crystallinity of 60–68% was observed for coatings heat treated at 450  Cin the presence of water vapor, and at 500  C and 600  C in the presence or absence of water vapor. In addition, increases in the degree of coating crystallinity were observed to be consistent with the increasing number of PO 4 peaks observed as a result of different post- deposition heat treatments. It was concluded that the presence of water vapor at 450  C post-deposition heat treatment significantly affect the crystallinity of CaP coatings, whereas an increase to temperature higher than 450  C and in the presence of water vapor has no significant effect on crystallinity. r 2003 Elsevier Ltd. All rights reserved. Keywords: Calcium phosphate coating; Heat treatment; X-ray diffraction; Crystallinity; Fourier transform infrared spectroscopy 1. Introduction Hydroxyapatite (HA) and calcium phosphate (CaP) coatings are successfully used in dental and orthopedic implant therapy [1]. The rationale for using HA or CaP coatings is to accelerate bone attachment and improve the strength of bonding between the metal and the bone, thus stabilizing the metal implants [2]. It is believed that the amorphous phase of the coatings, which has a greater resorption in vivo than crystalline HA coatings [1–3], can accelerate the early fixation of the implant with the bony tissue and promote fast bone remodeling and attachment. However, it is also known that a high concentration of amorphous phase in the coating can cause excessive dissolution and consequently reduce the coating integrity of the implants [4,5]. Extensive in vitro and in vivo research also suggested that the crystallinity of CaP and HA coatings is essential to their biocompa- tible and early performance when compared to non- coated titanium (Ti) implants [1,6–13]. Problems with plasma-sprayed HA coatings have also been well document [1,14–18]. As such other experi- mental coating processes have been investigated. It has been reported that sputtering may be the method of ARTICLE IN PRESS *Corresponding author. Health Science Center at San Antonio, Department of Restorative Dentistry, Division of Biomaterials, The University of Texas, 7703 Floyd Curl Drive, San Antonio, TX 78284- 7890, USA. Tel.: +1-2310-567-3676; fax: +1-210-567-3669. E-mail address: ong@uthscsa.edu (J.L. Ong). 0142-9612/$-see front matter r 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0142-9612(03)00459-9