The influence of strontium doping on the crystal morphology of synthetic calcium phosphates

Calcium phosphate crystals were synthesized via chemical precipitation with strontium (Sr) ionic doping, and starting solutions with at.% Sr 19 % (A), 40 % (B), and 53 % (C) in an acid environment (pH 6.0), resulting in the crystal without Sr with plate morphologies, sample A: Sr similar to 7.8 % and Ca similar to 92,2 % with plate+petaloid crystals, sample B showed two morphological groups: Sr similar to 12,5 % and Ca similar to 87,5 % (B-1) with plate+petaloid crystals and with Sr similar to 32,5 % and Ca similar to 67,9 % (B-2) with petaloid+pseudo-hexagons crystals, and sample C: Sr similar to 48,8 % and Ca similar to 51,2 % with higher symmetric hexagonal crystals. The samples were characterized by X-ray diffraction, SEM, and EDS. The calcium phosphate crystallographic phase family (Ca-P) includes brushite (DCPD), monetite (DCPA), and hydroxyapatite (HAP) surrounding the nucleating crystals that had plate, petaloid, and pseudo-hexagonal or hexagonal morphologies. Crystal growth nucleation by Sr inclusion ions induces preferential orientation with overlapping layer plates forming pseudo-hexagonal or hexagonal crystals with high symmetry when there is ion equilibrium between Ca and Sr. This result indicates biomimicry crystals found in nature (abalone gastropod shell), resulting in promising materials for further advances in mechanical properties and performance.