posted on 2021-07-28, 10:43authored byAgne Kizalaite, Inga Grigoraviciute-Puroniene, Dane Romar C. Asuigui, Sarah L. Stoll, Sung Hun Cho, Tohru Sekino, Aivaras Kareiva, Aleksej Zarkov
In the present work,
a series of zinc whitlockite (CaxZny(HPO4)2(PO4)12) powders was synthesized by
a low-temperature dissolution–precipitation process for the
first time. The phase conversion from calcium hydroxyapatite to zinc
whitlockite occurred in an acidic medium in the presence of Zn2+ ions. Variable chemical composition of the synthesis products
was achieved by changing Ca-to-Zn molar ratio in the reaction mixture.
Investigation of the phase evolution as a function of time demonstrated
that phase-pure zinc whitlockite powders can be synthesized in just
3 h. It is also demonstrated that single-phase products can be obtained
when the Ca-to-Zn ratio in the reaction medium is in the range from
9 to 30. With higher or lower ratios, neighboring crystal phases such
as scholzite or calcium hydroxyapatite were obtained. The morphology
of the synthesized powders was found to be dependent on the chemical
composition, transforming from hexagonal to rhombohedral plates with
the increase of Zn content. Thermal stability studies revealed that
the synthesized compounds were thermally unstable and decomposed upon
heat treatment.