FUNDAMENTALS OF HYDROXYAPATITE AND RELATED CALCIUM PHOSPHATES - Advanced Biomaterials: Fundamentals, Processing, and Applications - page 31

(a)

O-H

21 112

PO 4 HPO 4 PO 4

A

O-H

v 1

v 4

v 3

300

xrd

002

CO 3
v 3

CO 3

26 30 34

v 2 B

202

210

102

201

C

(b)

D

Diff angle 2 θ

(c)

4000
Frequency, cm -1

3000 2000 1200 1000 800 600 400

b

(d)

26
Diffraction angle, °

30 34 2 θ

a

Figure 2.6. X-ray diffraction profi les of apatites prepared at 95 °C (6a) and 37 °C (6b) with in-
creasing ion concentrations in solution and in the apatite. With apatites prepared at 95 °C (a),
increasing carbonate, broadening of x-ray diffraction peaks indicate decrease in crystallite size
and shift in diffraction peaks indicate changes in lattice parameters caused by CO 3 incorpora-
tion in the apatite. At 37 °C, high carbonate concentration promotes the formation of carbon-
ate containing amorphous calcium phosphate, ACP, shown by the absence of diffraction peaks
and lack of resolution in the phosphate band (6bD) [55,59,87,126].

The type (i) and (ii) carbonate confi guration are associated with the conven-
tional type A infrared carbonate absorption bands at 1451 and 1540 cm − 1 , while
the type (iii) confi guration is associated with carbonate absorption bands at 1506
and 1571 cm − 1 (Figure 2.4) [22,24,57,83]. The type (iii) confi guration is a high-
pressure feature. On the other hand, Rietvelt X-ray structure analysis using
hydrothermally synthetic carbonate apatite powders indicated that CO 3 planes
are parallel to the c - axis in CO 3 - for - PO 4 substitution [44] .