Sinterability of Hydroxyapatite-Zirconia Composite Powder

無機マテリアル,Vol. 3, Mar. 102-110 (1996)

論文

Sinterability of Hydroxyapatite-Zirconia Composite Powder

Prepared by Double Nozzle Spray Pyrolysis

Kiyoshi ITATANI, Mamoru AIZAWA, Hiroyuki KANO,

F. Scott Howell and Akira KISHIOKA. (Department of Chemistry, Faculty of Science and Engineering, Sophia University,

7-1 Kioi-cho Chiyoda-ku, Tokyo 102 JAPAN)

Five kinds of hydroxyapatite (Ca10 (PO4) 6 (OH) 2) -zirconia (ZrO2) composite powders

were prepared by a double nozzle spray pyrolysis; the solutions of (a) 0.50 mol •E dm-3 Ca

(NO3)2 and 0.30 mol •E dm-3 (NH4)2HPO4 with Ca/P =1.67 and of (b) 1.2125•`9.7000 •~

10-2mol•E dm-3 ZrOCl2 and 0.75•`6.00 •~ 10-4 mol•E dm-3 YCl3 with Y2O3/ (ZrO2+ Y2O3)

= 0.03 were simultaneously spray-pyrolysed in the hot zone of the electric furnaces heatedat 600•Ž, using two air-liquid nozzles. The sinterabilities of these composite powders were

examined by two techniques: pressureless sintering and hot-pressing techniques. The

resulting powders had the (ZrO2+Y2O3) contents ranging from 9.71 to 79.42 mol%; such

(ZrO2+Y2O3) content could be controlled by changing the concentration of the solution in

the ZrOCl2-YCl3 system. The relative density of the compact fired at 1100•Ž for 5 h

decreased from•`95% down to•`65% with (ZrO2+Y2O3) content. In order to fabricate

the dense ceramics, the composite compacts were hot-pressed at 1100•Ž for 1 h. The rela-

tive density of the hot-pressed compact containing 9.71 mol% of the (ZrO2+Y2O3) con-

tent attained 99.0%. The crystalline phases of these hot-pressed compacts were HAp,

tetragonal ZrO2 and a small amount of ƒÀ—Ca3 (PO4)2. The small ZrO2 grains with sizes of-

0.1 ,ƒÊm were homogeneously dispersed not only on grain boundaries but also within HAP/

β-Ca3 (PO4) 2 grains.(Received Oct. 13, 1995) (Accepted Oct. 30, 1995)

Key words: Hydroxyapatite, Zirconia, Composite Powder, Double Nozzle Spray Pyroly-sis, Sinterability

1 Introduction

Spray pyrolysis is one of the excellent tech-niques for preparing the easily-sinterable ceram-ic powders, where the droplets containing thedesired kinds and amounts of component ionsare spray-pyrolysed in the hot zone of the elec-tric furnace. Since the ceramic powders may be produced instantaneously through the evapora-tion of solvents, thermal decompositions of metal salts and reactions of metal salts/oxides, they generally have the characteristics of (i) sub-micrometer-sized primary particles, (ii) narrow primary particle size distributions and (iii) little segregation of the components') . By making use of this technique, the present authors prepared

various calcium phosphates: hydroxyapatite

(Ca10 (PO4) 6 (OH) 2; HAp) 2) , ƒÀ-calcium ortho-

phosphate (ƒÀ-Ca3 (PO4) 2) 3) y-calcium diphos-

phate (y-Ca2P2O7) 4) ,5) and .ƒÂ-—calcium metaphos-

phate (ƒÂ-Ca (PO3) 2) 4),5) .

Among the calcium phosphates, apatite is an

attractive material for bone and tooth implant;

however, the applications of apatite to the practi-

cal uses are restricted, chiefly due to insufficient

mechanical strengths. In order to improve such

mechanical strengths, attention has been direct-

ed toward the composites of zirconia (ZrO2)

especially yttria (Y2O3) stabilized tetragonal

ZrO2 polycrystals (Y-TZP) , with HAp6)-9) or

apatite (Ca10 (PO4) 6 (O, F2) ) -containing glass-

ceramics10) -12) . Unfortunately, the conventional

102

Inorganic Materials, Vol. 3, Mar. (1996)

spray-pyrolysis technique is not suitable for the

preparation of such composites, because the for-

mation of precipitates in the starting solutions

makes the homogeneous spray pyrolysis

difficult. In order to prepare the composite pow-

ders, the present authors assembled a novel

apparatus equipped with two nozzles. By using

this apparatus, the authors demonstrated that

HAp-ZrO2 composite powders can be instantane-

ously prepared without a mixing operation;13)

however, no systematical information on prepa-

ration conditions of HAp-ZrO2 composite pow-

ders and on sinterabilities of the resulting pow-

ders has been available yet. The purposes of this

research are (i) to prepare the HAp-ZrO2 compo-

site powders by "double nozzle" spray pyrolysis

and (ii) to examine the sinterabilies of the result-

ing composite powders.

2 Experimental

2•E1 Reaction apparatus and preparation of

composite powders

Figure 1 shows the overall view of the spray

pyrolysis apparatus. The reaction apparatus was

composed of a spraying zone, a heating zone and

a powder collecting zone. Each zone will be

explained below:

(I) Spraying zone ( (a) -(e)

The starting solutions were prepared as fol-

lows: (i) the nitric acid solution containing calci-

um nitrate (Ca (NO3) 2) and diammonium hydro-

gen orthophosphate ( (NH4) 2HPO4) ) with Ca/

P=1.672) and (ii) the solution containing zirconi-

um oxychloride (ZrOCl2) and yttrium chloride

(YCl3) with Y2O3/ (ZrO2 + Y2O3) = 0.03. The

concentrations of these solutions are listed in

Table 1. The droplets in the Ca (NO3) 2- (NH4) 2

HPO4 system ( (a) ) and those in the ZrOCl2 and

YCl3 system ((b)) , both of which are formed by

air-liquid nozzles ((d)) , were separately

introduced into the fused silica tube ( (f) : I.D. 80 mm and height 1.5 m) through the double tubes ((e)) , using compresser ( (c) ; flow rate; 10 dm3.min-1) . (II) Heating zone ( (f) (h) )

The dropets in the Ca (NO3) 2- (NH4) 2HPO4 system and those in the ZrOCl2-YCl3 system

Fig. 1 Overall view of spray-pyrolysis apparatus. (a): Solution for preparing HAp, (b); Solu-tion for preparing Y-TZP, (c): Compressor,

(d): Liquid-air nozzle, (e). Double tube, (f): Silica tube, (g): Electric furnace, (h): Ther-mocouples, (i): Test-tube type filter, (j): Lie-big condensor, (k): Aspirator.

Table 1 Preparation conditions of the starting solutions.

103

無機マテリアル,Vol. 3, Mar. (1996)

were spray-pyrolysed in the electric furnace

((g)). The spray-pyrolysis temperature was

fixed to be 600•Ž; the temperature was recorded

by the thermocouples ( (h) ) placed in the center

of the fused silica tube.

(III) Collecting zone ( (i) (k)

The resulting powders and evolved gas were

collected by a test-tube type filter ((i)) and Lie-

big condenser (j) , using aspirator ( (k) ) . The

resulting powders were calcined at 600•Ž for 1 h

and then pulverized using zirconia mortar and

pestle; the powders were composed of the prima-

ry particles with sizes of•` 0.1ƒÊm13).

2•E2 Phase identification and quantitative

analysis

The crystalline phases were examined using

an X-ray diffractometer (XRD; 40 kV, 25 mA)

with Ni-filtered CuKa radiation. The quantita-

tive analyses of the calcined powders were

conducted using an X-ray fluorescence appara-

tus (XRF; Model SFX-1200, Shimadzu, Kyoto) .

2.3 Dilatometry

The cylindrical compacts with diameters of 5

mm and thickness of-3 mm were fabricated by

pressing-0.15 g of composite powders uniaxial-

ly at 267 MPa. The expansion-shrinkages of

composite compacts were measured from room

temperature up to 1300•Ž at the heating rate of

10•Ž •E min-1, using thermomechanical analyser

(TMA; Model TAS 100, Rigaku, Tokyo) .

2.4 Sintering of the compacts

The cylindrical compacts with diameters of

20 mm and thickness of-2 mm were fabricated

by pressing-1.5 g of powders uniaxially at 50

MPa. The compacts were fired at 1100•Ž for 5 h;

the heating rate was 10•Ž •E min-1. Moreover, the

compacts were hot-pressed at 1100•Ž for 1 h

under the pressure of 30 MPa; the heating rate

was 5•Ž •E min-1. After hot-pressing for the

desired time, the compacts were cooled down to

300•Ž at the rate of 5•Ž •E min-1 and then the elec-

tric power was turned off.

2.5 Microstructural evaluation

The polished surfaces of the hot-pressed com-

pacts, after being etched thermally at 50•Ž lower

than the firing temperature, were observed

Fig. 2 X-ray diffraction patterns of the resulting pow-

ders.

Table 2 Compositions of the sample powders prepared by spray pyrolysis.

104


using a scanning electron microscope (SEM;

Model S-4500, Hitachi, Tokyo) and an atomic

force microscope (AFM; Model TMX-2000,

TopoMetrix, Santa Clara, CA, USA) .

3 Results and discussion

3•E1 Crystalline phases of the resulting pow-

ders

Figure 2 shows the XRD patterns of the cal-

cined powders. The crystalline phases in Sample

Nos. 2 to 4 were HAp14) and tetragonal Zr0215)

(Y-TZP) ; however, Sample No. 1 contained a

small amount of ƒÀ-Ca3 (PO4)216), together with

HAp and Y-TZP.

The compositions of the powders are exa-

mined on the assumption that the crystalline

phases are HAp and Y-TZP; the presence of ƒÀ-

Ca3 (PO4)2 in Sample No. 1 is neglected, partly

because the amount of such ƒÀ-Ca3 (PO4) 2 is very

small, and partly because the Ca/P ratio

( = 1.66) of Sample No. 1 is almost in accord

with that ( =1.67) of the stoichiometric HAp. In

fact, our previous data obtained by the conven-

tional "single nozzle" spray pyrolysis technique

shows that the stoichiometric HAp can be even-

tually obtained by the heat-treatment of the

spray-pyrolysed powders, even though fl—Ca3

(PO4)22) is present in the powders.

The compositions of the sample powders are

listed in Table 2. Reflecting the X-ray intensi-

ties of HAp and Y-TZP, the amount of HAp

decreased with (ZrO2 + Y2O3) content. Here-

after four kinds of composites will be designated

as HZ (9.71) , HZ (19.32), HZ (39.51) and

HZ (79.42) , respectively; the numbers in the

parentheses indicate (ZrO2 + Y2O3) contents.

As the above results indicate, most of the

droplets in the Ca (NO3) (NH4)2HPO4 system

and those in the ZrOC12-YCl3 system seem to be

separately spray-pyrolysed in the hot zone of the

electric furnace, because the compounds in the

CaO—P2O5—ZrO2-Y2O3 system were not detected

from the powder. Thus the present double noz-

zle spray-pyrolysis technique is suitable for

preparing the HAp-ZrO2 composite powders.

3•E2 Pressureless sintering of composite

powders

First of all, the densification processes of the

composite compacts were examined using

TMA. Figure 3 shows the typical shrinkage

curve and the derivative curve (shrinkage rate)

of HZ (79.42) compact, together with those of

pure HAp compact. A comparison of the shrink-

age and shrinkage-rate curves of HZ (79.42)

compact with those of HAp compact revealed

(a)

(b)

that the shrinkage behavior could be classified

into two regions, i.e., (i) 600•Ž to 1050•Ž and

(ii) 1050•Ž to 1300•Ž, according to the heating

temperature. In range (i), 600•Ž to 1050•Ž, the

shrinkages of HZ (79.42) compact were higher

than those of HAp compact. Reflecting this

shrinkage behavior, the shrinkage-rate curve

showed that a maximal value appeared at

～750℃. The maximal value in the shrinkage-

rate curve of HZ (79.42) compact appeared at

almost the same temperature as in the case of

HAp compact; however, the former maximal

value (•`0.3% -min-1) was higher than the lat-

ter value (•`0.1% -min-1).

The above densification behavior of

HZ (79.42) compact may be associated with the

solid-state reaction of HAp with Y-

TZP6)•`8),13),17)•`19). A part of HAp is decom-

posed to form ƒÀ-Ca3 (PO4)2 in the presence of

Y-TZP:

(1)

The liberated CaO seems to be solid-soluted into Y-TZP (Ca-Y-TZP) 6)-8) ,13) '17) -19) . The acceler-ated shrinkage rate of HZ (79.42) compact at～750℃ may, therefore, be attributed to the pro-

motion of the mass transfer due to the decompo-

sition of HAp.

Fig. 3 (a) Shrinkage curves and (b) shrinkage-rate

(S.R.) curves of (----) HAp compact and

(•\) HZ (79.42) compact at the heating

rate of 10•Ž•Emin-1.

105


In range (ii) , 1050•Ž to 1300•Ž, the shrink-

ages of HZ (79.42) compact were lower than

those of HAp compact. Reflecting these shrink-

age behaviors, the maximal shrinkage rate of

HAp compact was achieved at•`1100•Ž , whereas the maximal shrinkage rate of

HZ (79.42) compact came at•`1200•Ž.

The shrinkages of HZ (79.42) compact are

lower than those of HAp compact, which sug-

gests that the mass transfer of HAp may be

inhibited by the presence of Ca-Y- TZP. In addi-

tion, since the small amount of ƒÀ-Ca3(PO4)2

transforms into ƒ¿-Ca3 (PO4)2 at•`1120•Ž , it

brings about the volume expansion3), thus reduc-

ing the shrinkages.

On the basis of the above results, the pressure-

less sintering of the composite powders was

performed at 1100•Ž for 5 h; this sintering tem-

perature was selected to avoid the transforma-

tion of ƒÀ-Ca3 (PO4)2 into ƒ¿-Ca3 (PO4)2 and to pro-

mote the densification (see the shrinkage-rate

data in Fig. 3) . Results are shown in Fig. 4,

together with the relative densities of the green

compacts. The relative densities of the green

compacts were•`50%, independent of the (ZrO2

+Y2O3) content. On the other hand, the relative

density of the sintered HAp compact was•`95%;

however, it decreased down to•`65% as the

(ZrO2+ Y2O3) content increased up to 79.42

(b)

(a)

mol%.

The above results reveal that the relative den-

sity of the composite compact may be reduced

with (ZrO2 + Y2O3) content. These relative den-

sities are almost comparable to those of the

composite compacts obtained by firing the com-

mercially-available HAp (Central Glass Co .,

Ltd.; Grade BN)–Y-TZP (Tosoh Corp.; TZ-

3Y) powder compacts at 1150•Ž for 5 h . Thus

the sintering temperatures of the present compo-

site powders may be•`50•Ž lower than those of

commercially-available powders.

In order to make clear the reduction of the

relative density with (ZrO2+ Y2O3) , the micros-tructures of these sintered compacts were

observed using SEM. Typical microstructure of

the sintered HZ (9.71) compact is shown in Fig .

5. The small grains with sizes of •`0.1 ,ƒÊm ( (a) ) were present at the edges of grains with sizes of

0.2 ,ƒÊm or larger ((b)) .

Although we tried to check the distribution

state of each element by using an energy-disper-

sive X-ray analyser, the overlapping of ZrLƒ¿ and

PKa spectra made the analysis difficult . Judging

from the fact that ZrO2 tends to appear brighter

due to the difference in atomic number12), we

think that the small grains with sizes of•`0.1 ƒÊm

correspond to Ca-Y-TZP. Such Ca-Y-TZP

grains may inhibit the mass transfer, thus allow-

ing the pores among HAp/ƒÀ-Ca3(PO4)2 grains

to remain.

3•E3 Hot-pressing of calcined powders

Since the relative density of the pressureless

sintered compact was reduced down to•`65%

with (ZrO2+ Y2O3) content up to 79 .42 mol%,

the composite compacts were hot-pressed at

Fig. 4 Changes in relative densities of (a) green

compacts and (b) compacts fired at 1100•Ž

for 5 h with (ZrO2+Y2O3) content.

Fig. 5 Typical SEM micrograph of HZ(9.71) com-

pact fired at 1100•Ž for 5 h.

106


1100•Ž for 1 h. The hot-pressing time (1 h) was

shorter than the pressureless sintering time (5

h) , because the dense ceramics could be fabricat-

ed under the present hot-pressing conditions.

Results are shown in Fig . 6. The relative density

of the hot-pressed HZ (9.71) compact was

99.0%, which was comparable to that of hot-

pressed HAp compact. The relative density of

the hot-pressed compact decreased down to-

88% as the (ZrO2 + Y2O3) content increased up

to 79.42 mol%.

Obviously, the relative densities of the hot-

pressed compacts were higher than those of the

pressureless sintered compacts. To fabricate the

dense ceramics with the relative densities of

above 99%, the (ZrO2+ Y2O3) content must be

restricted to be•`10 mol%.

The crystalline phases of the hot-pressed

compacts were examined using XRD. Typical

XRD pattern of hot-pressed HZ (79.42) is shown

in Fig. 7. The XRD pattern showed that the crys-

talline phases were HAp, tetragonal ZrO2 and ƒÀ-

Ca3 (PO4) 2.

In order to examine the dispersion state of

Ca-Y-TZP grains in the HAp matrix, the micros-

tructures of the hot-pressed compacts were

examined using SEM. Typical SEM micro-

graphs of the compacts hot-pressed at 1100•Ž

for 1 are shown in Fig . 8. The SEM micrograph

of the hot-pressed HAp compact (Fig. 8 (a) )

showed that the polyhedral grains with sizes of

0.5•`3 pm were packed closely. The SEM micro-

graph of the hot-pressed HZ (9.71) compact

(Fig. 8 (b) ) showed that the grains with sizes of

0.5•`2 pm were packed closely; moreover, the

small grains with sizes of•`0.1 ƒÊm were dis-

persed not only on grain boundaries but also

within grains. The SEM micrograph of the hot-

pressed HZ (19.32) compact (Fig. 8 (c) ) indicat-

ed that the microstructure was similar to that of

the hot-pressed HZ (9.71) compact; however,

the polyhedral grain sizes (0.5•`1 pm) were

somewhat smaller than those of HZ (9.71) com-

pact. The SEM micrograph of the hot-pressed

HZ (79.42) compact (Fig. 8 (d) ) showed that

the polyhedral grains with sizes of 0.2•`1 ƒÊm

were packed closely; the grains with sizes of

0.5•`1 ƒÊm, which were composed of the small

grains with sizes of•`0.1 ƒÊm, were present;

moreover, such small grains were also present

on grain boundaries.

As stated before, the polyhedral grains with

sizes of 1•`2 pm correspond to HAp and ƒÀ—Ca3

(PO4) 2, whereas the small grains with sizes of

0.1 pm correspond to Ca-Y-TZP. Since the Ca-

Y-TZP grains are homogeneously dispersed in

the HAp/ƒÀ-Ca3 (PO4)2 matrix, these composite

compacts are expected to have high mechanical

strength6),8),9). The grain sizes of HAp are

reduced with (ZrO2 + Y2O3) content, which

proves that the mass transfer of HAp is inhibited

by the presence of such Ca-Y-TZP grains. In

order to confirm this assumption, the microstruc-

tures of the hot-pressed compacts were

examined using AFM. A typical AFM image of

the hot-pressed HZ (9.71) compact is shown in

Fig . 9. Although two grains with sizes of-0.2

pm were linked to each other ( (a) ) , the grain

growth was disturbed by the grains with sizes

of•`0.1 pm ( (b)).

Referring to the previous SEM micrographs,

the grains with sizes of•`0.2 ƒÊm ( (a) ) may

Fig. 6 Changes in relative densities of the compacts

hot-pressed at 1100•Ž for 1 h with (ZrO2+Y2

O3)content.

Fig. 7 Typical XRD pattern of HZ(79.42) compact

hot-pressed at 1100•Ž for 1 h.

○:HAp,〓:β-Ca3(PO4)2,□:tetragonal

ZrO2.

107


correspond to HAp and ƒÀ-Ca3(PO4)2, whereas

the grains with sizes of•`0.1 ,ƒÊm ( (b) ) cor-

respond to Ca-Y-TZP. The grain growth of

HAp is disturbed by the Ca-Y-TZP grains,

which demonstrates that such Ca-Y-TZP grains

may inhibite the mass transfer of HAp and ƒÀ-

Ca3 (PO4) 2.

Futhermore, the atomic-scale image of the

hot-pressed HZ (9.71) compact was obtained

using AFM. A typical AFM image of the hot-

pressed HZ (9.71) compact is shown in Fig. 10.

The interatomic distance shown in the figure

was 0.317 nm, which corresponded to the (102)

plane of HAp. Although most of the atoms had a

high degree of crystal order, some lattice disord-

er appeared to be present in the crystal structure

(see arrow marks) .

As the above AFM image indicates, the lattice

disorder may be present on the surfaces of the

Fig. 8 SEM micrographs of (a) HAp compact, (b) HZ (9.71) compact, (c) HZ (19.32) compact and (d)

HZ (79.42) compact hot-pressed at 1100•Ž for 1 h.

Fig. 9 Typical AFM image of HZ (9.71) compact

hot-pressed at 1100•Ž for 1 h.

108


hot-pressed compact. Although the atomic-scale

AFM image of HAp has been obtained by

Siperko and Landis20), no lattice disorder was

observed in the crystal structure. The probable

explanation for the presence of the lattice disord-

er is that numerous vacancies are created by the

partial decomposition of HAp in the presence of

ZrO2 18),19). Some further investigation is,

however, needed to make clear the presence of

this disorder.

4 Conclusion

Five kinds of hydroxyapatite (Ca10 (PO4)6

(OH)2; HAp) -zirconia (ZrO2) composite pow-

ders were prepared by the double nozzle spray-

pyrolysis technique, i.e., the simultaneous spray

pyrolysis of solution in the Ca (NO3) 2- (NH4) 2

HPO4 and that in the ZrOCl2-YCl3 system, using

two nozzles. The compressed powders were

examined by two techniques: pressureless sinter-

ing and hot-pressing techniques. The results

were summarized as follows:

(1) The double nozzle spray-pyrolysis made

the preparation of HAp-ZrO2 composite

powders possible. The resulting powders had

the (ZrO2+ Y2O3) content ranging from 9.71 to

79.42 mol%.

(2) When the composite compacts were fired

at 1100•Ž for 5 h, the relative density of the

sintered compact decreased from•`95% down

to-65% with (ZrO2+ Y2O3) content up to

79.42 mol%. In order to fabricate the dense cer-

amics, the composite compacts were hot-

pressed at 1100•Ž for 1 h. The relative density of

the hot-pressed compact with (ZrO2 + Y2O3) con-

tent of 9.71 mol% attained 99.0%; however, the

relative density decreased down to•`88% with

(ZrO2+ Y2O3) content up to 79.42 mol%. The

small grains with sizes of•`0.1 ƒÊm were homoge-

neously dispersed not only on grain boundaries

but also within HAp and ƒÀ-Ca3 (PO4) 2 grains.

Acknowledgements

The authors wish to express their thanks to

Mr. S. Ando for assembling glass parts of the

spray-pyrolysis apparatus.

References

1) K. Itatani, A. Kishioka, M. Kinoshita,

Gypsum & Lime, No. 241, 25 (1992)719.

2) K. Itatani, O. Takahashi, A. Kishioka,

M. Kinoshita, Gypsum & Lime, No. 213,

19 (1988) .

3) K. Itatani, T. Nishioka, S. Seike, F. S.

Howell, A. Kishioka, M. Kinoshita, J.

Am. Ceram. Soc., 77, 801 (1994) .

4) K. Itatani, M. Aizawa, F. S. Howell, A.

Kishioka, M. Kinoshita, Phosphorus Res.

Bull., 1, 35 (1991) .

5) M. Aizawa, K. Itatani, Y. Miyamoto, A.

Kishioka, M. Kinoshita, Gypsum & Lime,

No. 237, 22 (1992) .

6) N. Tamari, M. Mouri, I. Kondo, Yogyo-

Kyokai-Shi 95, 806 (1987).

7) J.-M. Wu, T.—S. Yeh, J. Mater. Sci., 23,

3771 (1988) .

8) K. Ioku, S. SOmiya, M. Yoshimura, J.

Ceram. Soc. Jpn., 99, 196 (1991) .

9) J. Li, L. Hermansson, R. Soremark, J.

Mater. Sci.: Mater. Med., 4, 50 (1993) .

10) T. Kasuga, K. Nakajima, T. Uno, M.

Yoshida, J. Am. Ceram. Soc., 75, 1103

(1992) . 11) T. Kasuga, M. Yoshida, A. Ikushima, M.

Tuchiya, H. Kusakari, J. Am. Ceram. Soc.

85, 1884 (1992) .

12) T. Kasuga, M. Yoshida, A. J. Ikushima,

M. Tuchiya, H. Kusakari, J. Mater. Sci.:

Mater. Med., 4, 36 (1993) .

13) S. Seike, K. Itatani, F. S. Howell, A.

Kishioka, M. Kinoshita, Trans. Mat. Res.

Fig. 10 High-resolution atomic-scale AFM image of

HZ (9.71) compact hot- pressed at 1100•Ž

for 1 h.

Arrow marks indicate the typical lattice dis-

order.

109


Soc. Jpn., 14A, 731 (1994).

14) Joint Committee on Powder Diffraction

Standards, No. 24-33, JCPDS-Interna-

tional Center for Diffraction Data, New-

town Square, PA, (1974).









17) N. Miura, M. Akao, H. Aoki, K. Kato,

Rep. Inst. Med. & Dent. Eng., 17,

21 (1983).

18) K. Yamashita, T. Kobayashi, T. Ume-

gaki, T. Kanazawa, Sintering 87', Ed. by S. Somiya, M. Shimada, M. Yoshi-

mura, R. Watanabe, Elesevier Applied

Science, London, (1987) p. 1320.

19) K: Yamashita, T. Kobayashi, M. Kita-

mura, T. Umegaki, T. Kanazawa, Sera-

mikkusu Ronbun Shi, 96, 616 (1988).

20) L. M. Siperko, W. J. Landis, J. Mater.

Sci. Lett., 12, 1068 (1993).

(1995.10.13受付)

(1995.10.30受理)

ダブルノズル噴霧熱分解法により調製した水酸アパタイトー

ジルコニア複合粉体の焼結性

板谷清司・相澤守・鹿野博之・F.Scott Howell・岸岡昭

(上智大学理工学部化学科)

5種類の水酸アパタイト(Ca10(PO4)6(OH)2;HAp)-ジルコニア(ZrO2)系複合粉体をダブルノズル噴霧熱

分解法によって調製した。すなわち,(a)0.50mol・dm-3Ca(NO3)2および0.30mol・dm-3(NH4)2HPO4が

Ca/P比1.67になるように調製した硝酸酸性溶液と,(b)1.2125～9.7000×10-2mol・dm-3ZrOCl2および

0.75～6.00×10-4mol・dm-3 YCl3がY2O3/(ZrO2+Y2O3)比0.03になるように調製した溶液とを2個のノズ

ルを用いて同時に噴霧熱分解して目的の化合物を調製した。えられた粉体の(ZrO2+Y2O3)含有量は9.71

mol%から79.42mol%の範囲にあった。これらの複合粉体の成形体を1100℃,1時間ホットプレスしたとこ

ろ,(ZrO2+Y2O3)含有量が9.71mol%の場合に相対密度が99.0%の高密度焼結体をえることができた。こ

の焼結体の結晶相はHAp,正方晶ZrO2および β-Ca3(PO4)2(少量)であった。また,HAp/β-Ca3(PO4)2の

結晶粒界および結晶粒内には約0.1μmのZrO2結晶粒が均質に分散していた。

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