was done at 1200 C. All other ionic substituted nanopowders showed a biphasic
mixture of hydroxyapatite and TCP at 1000 C and 1200 C (Table 23.6).
SiHA and KSiHA nanopowders heat-treated at 800 C showed both HA and
α-TCP as major phases with β-TCP as the secondary phase. Although α-TCP and
HA are primary phases in potassium and silicon co-substituted HA (KSiHA)
nanopowder, the fraction of α-TCP decreased in KSiHA nanopowder in comparison
to SiHA nanopowder. The fraction of β-TCP phase increased in the case of KSiHA
nanopowder with respect to SiHA nanopowder. With an increase in heat treatment
temperature, the calculated weight % of TCP phase increased. The order of structural
stability is as follows:
FHA > HA > ZnFHA > KSiHA > ZnHA > EuHA > MgSrHA > SiHA
> SrFHA > MgSrFHA > MgHA
Fourier transform infrared spectra were recorded in the region 400–4000 cm1
using KBr pellets (1%, wt/wt) with a spectral resolution of 2 cm1 to identify the
various functional groups present in nanodimensional powders of HA such as
phosphates, carbonates, hydroxyl, and nitrates. Figure 23.6 shows the characteristic
peaks exhibited by the FTIR spectra of as-synthesized nanopowder. The FTIR
spectrum of as-synthesized HA nanopowder showed all the specific peaks of pure
HA, i.e., phosphate vibrations, ν1 PO4
3 (962 cm1), ν2 PO4
3 (473 cm1), ν3
PO4
3 (broad band 1031–1093 cm1), and ν4 PO4
3 (569 cm1 and 602 cm1), and
hydroxyl group of hydrogen bonded to OH at 3569 cm1 and 631 cm1. The peak
at 874 cm1 could be attributed to P-O-H vibration in HPO4
2. Broad envelop
between 3446 cm1 and 3242 cm1 and absorption bands between 2076-2001 cm1
and at 1636 cm1 could be attributed to O-H and H-O-H vibrations of absorbed
water molecules in HA crystal structure, respectively.
The FTIR spectra of ZnHA nanopowder were similar to HA but with decreased
strength of OH vibrational mode at 3569 cm1 and 630 cm1 and PO4
3
Table 23.6 Weight % of HA and TCP phases in heat-treated nanopowders from XRD patterns
Nanopowder
Weight % HA
Weight % β-TCP and α-TCP
800 C
1000 C
1200 C
800 C
1000 C
1200 C
HA
100.00
100.00
77.00
0.00
0.00
23.00
ZnHA
84.60
67.50
50.82
15.40
32.50
49.18
MgHA
51.00
42.00
35.00
49.00
58.00
65.00
EuHA
83.50
67.24
59.45
17.50
32.76
40.55
FHA
100.00
100.00
87.00
0.00
0.00
13.00
SiHA
73.83
72.44
62.70
5.37, 20.44
11.09, 16.47
20.38, 16.91
KSiHA
84.99
73.79
69.99
6.52, 8.49
12.81, 13.41
21.37, 8.64
ZnFHA
100.00
92.23
63.48
0.00
7.76
36.52
SrFHA
73.00
72.00
71.00
27.00
28.00
29.00
MgSrHA
77.00
75.00
69.00
23.00
25.00
31.00
MgSrFHA
60.00
47.00
44.00
40.00
53.00
56.00
23
Unleashing Potential of Bone Mimicking Nanodimensional Hydroxyapatites and. . .
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