Synthesis and characterization of strontium-doped hydroxyapatite for biomedical applications Yıldız Yaralı O ¨ zbek 1 • Fatih Erdem Bas ¸tan 1 • Fatih U ¨ stel 1 Received: 12 February 2016 / Accepted: 1 June 2016 Ó Akade ´miai Kiado ´, Budapest, Hungary 2016 Abstract The aim of this study was to investigate the effect of strontium (Sr) doping into hydroxyapatite (HA) powders. It is well known that strontium promotes bone formation, reduces bone resorption and it is used to treat osteoporotic diseases as stated previously by researchers. Strontium-doped HA (Sr–HA) was produced by precipita- tion with increasing amount of ion exchange between calcium (Ca) and Sr. Two different Sr amounts as 2 and 4 mol% were doped into HA by adding Sr(NO 3 ) 2 to the reaction solution. The precipitated HA was separated from supernatant after the vacuum filtration. The filtered wet cake of HA was exposed to spray drying and calcined in an air furnace at 1200 °C. The produced-HA powders were analyzed by using SEM, FTIR, XRD and TG–DSC tech- niques. At the end of the study, the results showed that decomposition of HA to tri-calcium phosphate increases with increasing Sr content. Thermal analyses revealed that Sr-doped HA powders loose more mass than pure HA powders. Keywords Strontium Á Hydroxyapatite Á Precipitation Á Thermal analyses Introduction Apatite family contains inorganic crystalline compounds and is shown with a general formula X 10 Y 6 Z 2 while usu- ally bivalent cations such as Ca 2? , Sr 2? , Pb 2? , monovalent and trivalent cations could also take the place of X, PO 4 3- and CO 3 2- is possible substitutions for Y. Monovalent anions such as OH - ,F - could take place Z. Due to excellent bioactivity, biocompatibility, insolubility and similarity to the natural bone, hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 ,HA) is used in biomedical application as a coating for fixation, filling material for bone defect [1–8]. Sr, one of the well-known bivalent cations, could be used for substitution with calcium in HA, due to the bio- logical benefits. It is used in osteoporosis treatment for many years, and the mineral structure of the bone possesses strontium, particularly at the sections of the elevated metabolic turnover [9–12]. Strontium (Sr) element could be found in calcareous rocks, the ocean water and a natural constituent of refreshments [13]. The most of the Sr content in the total body is located in the bone tissue, and it is a natural bone- seeking element due to its physical and chemical structure resemblance to calcium [14]. Additionally, researchers have pointed out the two efficacies of strontium ions to increase bone formation and decrease the bone resorption. Strontium could be substituted with calcium in the whole range of composition in the HA structure [15–20]. Until this time, substitutions in HA have been made in order to assimilate the structure to chemical composition of the natural bone, improving biological, mechanical and antibacterial properties or decreasing solubility [11, 20–27]. The addition of Sr in bone crystal leads to larger dis- tance of Sr–OH than Ca–OH due to the larger ionic & Yıldız Yaralı O ¨ zbek yyarali@sakarya.edu.tr Fatih Erdem Bas ¸tan febastan@sakarya.edu.tr 1 Thermal Spray R&D Laboratory, Metallurgical and Materials Engineering Department, Sakarya University, Esentepe Campus, 54187 Sakarya, Turkey 123 J Therm Anal Calorim DOI 10.1007/s10973-016-5607-3