Formation of Ca–Zn–Na phosphate bioceramic material in thermal processing of EDTA sol–gel precursor Irma Bogdanoviciene • Marina Cepenko • Rainer Traksmaa • Aivaras Kareiva • Kaia To ˜nsuaadu Received: 23 September 2014 / Accepted: 28 January 2015 Ó Akade ´miai Kiado ´, Budapest, Hungary 2015 Abstract In this study, investigation of the Ca–P–O, Ca:Zn–P–O, Ca:Na–P–O, and Ca:Zn:Na–P–O precursor gels prepared using EDTA as complexing agent and slightly different starting materials was performed. For this purpose, thermal decomposition of the gels was studied by TG/DTA-EGA/MS with following evolvement of H 2 O, CO 2 , NH 3 , and NO x gases. Besides, thermal decomposition products were characterized by Fourier transform infrared spectroscopy, X-ray diffraction analysis, and scanning electron microscopy. It was demonstrated that thermal decomposition of Ca–P–O acetate and Ca:Zn–P–O, Ca:Zn:Na–P–O acetate-nitrate gels is different. Thus, the results of thermal decomposition of Ca:Zn–P–O and Ca:Zn:Na–P–O gels showed that Zn and Na additives ac- celerate decomposition of the gels. In addition, Na substi- tution at Ca sites creates conditions for the formation of the orthophosphate composites at lower temperatures. Keywords Calcium orthophosphates Á Sol–gel Á Substitution effects Á Thermal decomposition Á TG/DTA-EGA/MS Introduction Calcium orthophosphates are of special significance for humans because they represent the inorganic part of normal (bones and teeth) and pathological (i.e., those appearing due to various diseases) calcified tissues in mammals. Therefore, due to chemical similarity to biological calcified tissues the majority of artificially prepared calcium orthophosphates possess remarkable biocompatibility and bioactivity. Biphasic, triphasic, and multiphasic calcium orthophosphates have been considered as biomaterials for the reconstruction of bone defects, dental, and orthopedic applications. In general, this concept is determined by ad- vantageous balances of more stable (frequently hydrox- yapatite) and more resorbable (typically tricalcium phosphates) phases of calcium orthophosphate composites, while the optimum ratios depend on the particular appli- cation [1]. In recent years, calcium phosphates, especially hy- droxyapatite and tricalcium phosphate, have attracted sig- nificant interest in simultaneous use as bone substitute and drug delivery vehicle, adding a new dimension to their application. Their biocompatibility and variable stoichio- metry, thus surface charge density, functionality, and dis- solution properties, make them suitable for both drug and growth factor delivery. Calcium phosphates matrices and scaffolds have been reported to act as delivery vehicles for growth factors and drugs in bone tissue engineering [2]. Most natural bio-apatites, as well as other components of the composite of orthophosphates, are non-stoichio- metric because of the presence of minor constituents of other cations (Mg 2? , Zn 2? , Na ? , Sr 2? , etc.) as well as anions (HPO 4 2– , CO 3 2– , or F - ). The traces of metal ions introduced into structure of phosphates change their phy- sical, chemical, and biological properties [3, 4]. The I. Bogdanoviciene (&) Á K. To ˜nsuaadu Laboratory of Inorganic Materials, Tallinn University of Technology (TTU), Ehitajate tee 5, 19086 Tallinn, Estonia e-mail: irma.bogdanoviciene@gmail.com M. Cepenko Á A. Kareiva Department of Inorganic Chemistry, Vilnius University, Naugarduko 24, 03225 Vilnius, Lithuania R. Traksmaa Centre for Materials Research, Tallinn University of Technology (TTU), Ehitajate tee 5, 19086 Tallinn, Estonia 123 J Therm Anal Calorim DOI 10.1007/s10973-015-4507-2