title: Peculiarities in thermal evolution of precipitated amorphous calcium phosphates with an initial Ca/P ratio of 1:1.
abstract: Thermal evolution of amorphous calcium phosphate (ACP) powder from a fast nitrate synthesis with a Ca/P ratio of 1:1 were studied in the range of 20-980 °C. The powder consisted of amorphous dicalcium phosphate anhydrate (CaHPO4) after heating to 200 °C. CaHPO4gradually condensed to amorphous calcium pyrophosphate Ca2P2O7(CPP) between 200 to 620 °C. Amorphous CPP crystallized at 620-740 °C to a metastable polymorph α'-CPP of the high-temperature phase α-CPP and β-CPP. The α'-CPP/ β-CPP phase ratio reached a maximum at 800 °C (60 wt% α'-CPP/40 wt% β-CPP), and α'-CPP gradually transformed to β-CPP at a higher temperature. Some β-TCP occurred at 900 °C, so that a three-phasic mixture was obtained in the powder heated to 980 °C. The occurrence of metastable α'-CPP is attributed to Ostwald's step rule, and a mechanism for β-TCP formation is proposed. The advantages of prospective biomaterials from these powders are discussed.
authors.affiliation: Physics of Solids Department, V.N. Karazin Kharkiv National University, 4 Svoboda Sq., Kharkiv, 61022, Ukraine. intercom@univer.kharkov.ua.
authors.forename: Zoltan
authors.identifier: http://orcid.org/0000-0002-3650-5110
authors.initials: Z
authors.lastname: Zyman
authors.affiliation: Institute of Inorganic Chemistry and Center for Nanointegration Duisburg-Essen (CeNIDE), University of Duisburg- Essen, Essen, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Epple
authors.affiliation: Physics of Solids Department, V.N. Karazin Kharkiv National University, 4 Svoboda Sq., Kharkiv, 61022, Ukraine.
authors.forename: Anton
authors.initials: A
authors.lastname: Goncharenko
authors.affiliation: Physics of Solids Department, V.N. Karazin Kharkiv National University, 4 Svoboda Sq., Kharkiv, 61022, Ukraine.
authors.forename: Dmytro
authors.initials: D
authors.lastname: Rokhmistrov
authors.affiliation: Institute of Inorganic Chemistry and Center for Nanointegration Duisburg-Essen (CeNIDE), University of Duisburg- Essen, Essen, Germany.
authors.forename: Oleg
authors.initials: O
authors.lastname: Prymak
authors.affiliation: Institute of Inorganic Chemistry and Center for Nanointegration Duisburg-Essen (CeNIDE), University of Duisburg- Essen, Essen, Germany.
authors.forename: Kateryna
authors.initials: K
authors.lastname: Loza
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry; D002118:Calcium / Q000737:chemistry*; D002130:Calcium Phosphates / Q000737:chemistry*; D003460:Crystallization; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007259:Infrared Rays; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D010758:Phosphorus / Q000737:chemistry*; D011208:Powders; D013696:Temperature; D014961:X-Ray Diffraction
chemical_list: D001672:Biocompatible Materials; D002130:Calcium Phosphates; D011208:Powders; C519480:amorphous calcium phosphate; C485817:beta-tricalcium phosphate; D010758:Phosphorus; D002118:Calcium