Cation substitution in β-tricalcium phosphate investigated using multi-nuclear, solid-state NMR

Calcium orthophosphates (CaPO 4 ): Occurrence and properties

“…Last, one should very briefly mention on existence of carbonated HA (Lafon et al 2008;Tonegawa et al 2010;Yahia and Jemal 2010;Silvester et al 2014;Fleet 2015), chlorapatite (Kannan et al 2007;García-Tuñón et al 2012;Zhao et al 2013), as well as on a great number of CaPO 4 with various ionic substitutions (CaPO 4 with dopants) (Pan and Fleet 2002;Rey et al 2006;Kannan et al 2008;Boanini et al 2010b;Shepherd et al 2012;Adzila et al 2012;Grigg et al 2014;Š upová 2015). In principle, any ion in CaPO 4 might be substituted by other ion(s).…”

“…Usually, the ion-substituted CaPO 4 are of a non-stoichiometric nature with just a partial ionic substitution and there are too many of them to be described here. Currently, this is a hot investigation topic; therefore, the readers are referred to the special literature (Pan and Fleet 2002;Rey et al 2006;Kannan et al 2008;Boanini et al 2010b;Shepherd et al 2012;Adzila et al 2012;Grigg et al 2014;Š upová 2015). In addition, there is a very good review, in which the structures of more than 75 chemically different apatites have been discussed (White and Dong 2003).…”

Vitrification of β-tricalcium phosphate in sodium aluminoborophosphate glass and the effect of Ga3+ substitution

“…Sm 3+ , La 3+ with high coordination numbers (7)(8) substitute onto the Ca(1,2,3) sites, whereas 'small' cations, substitute onto the Ca(4,5) sites [24]. Cations relevant to the current study have been shown to substitute onto Ca(5) (Al 3+ , Ga 3+ ) and Ca(4) (Na + ) [24].…”

“…Ca(1,2,3; 18b) have seven or eight oxygen nearest neighbours; Ca(5; 6a) has six oxygen nearest neighbours; Ca(4; 6a) is observed to be only partially filled, with an occupancy of 0.5 calculated by charge balancing, and is displaced significantly towards one face of the surrounding oxygen octahedron, resulting in 3 oxygen nearest neighbours at 2.53 Å with 3 more at 3.12 Å and a further 3 at 3.25 Å. Bond-valence analysis on the structure also reveals a dramatic under-bonding of this site [12]. A model attempting to explain the substitution mechanisms for monovalent, divalent and trivalent cations has been proposed [8,24], and it has been suggested, both from numerical calculations [25] and experimental observations, that 'large' cations, e.g. Sm 3+ , La 3+ with high coordination numbers (7)(8) substitute onto the Ca(1,2,3) sites, whereas 'small' cations, substitute onto the Ca(4,5) sites [24].…”

“…A model attempting to explain the substitution mechanisms for monovalent, divalent and trivalent cations has been proposed [8,24], and it has been suggested, both from numerical calculations [25] and experimental observations, that 'large' cations, e.g. Sm 3+ , La 3+ with high coordination numbers (7)(8) substitute onto the Ca(1,2,3) sites, whereas 'small' cations, substitute onto the Ca(4,5) sites [24]. Cations relevant to the current study have been shown to substitute onto Ca(5) (Al 3+ , Ga 3+ ) and Ca(4) (Na + ) [24].…”