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Characterization of calcium phosphate coatings doped with Mg, deposited by pulsed laser deposition technique using ArF excimer laser
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Micron 40 (2009) 140–142 www.elsevier.com/locate/micron
Characterization of calcium phosphate coatings doped with Mg, deposited by pulsed laser deposition technique using ArF excimer laser W. Mro´z a, M. Jedyn´ski a,*, A. Prokopiuk a, A. S´lo´sarczyk b, Z. Paszkiewicz b b
a Institute of Optoelectronics, Military University of Technology, Kaliskiego 2, 01-489 Warsaw, Poland AGH-Faculty of Material Science and Ceramics, University of Science and Technology, Al. Mickiewicza 30, 30-059 Krakow, Poland
Received 25 October 2007; received in revised form 18 January 2008; accepted 21 January 2008
Abstract Calcium phosphate layers were deposited on Ti6Al4V substrates with TiN buffer layers by use of pulsed laser deposition method. With this technique three pressed pellets consisted of tricalcium phosphate (TCP, Ca3(PO4)2), hydroxyapatite (HA, Ca10(PO4)6(OH)2) and hydroxyapatitedoped with magnesium (HA with 4% of Mg and trace amount of (Ca,Mg)3(PO4)2) were ablated using ArF excimer laser (l = 193 nm). The using of different targets enabled to determine the influence of target composition on the nature of deposited layers. The obtained deposits were characterized by means of Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction method (XRD). The obtained Fourier spectras revealed differences in terms of intensity of spectral bands of different layers. The analysis from XRD showed that Mg-doped HA layer has crystalline structure and TCP and HA layers composition is characterized by amorphous nature. # 2008 Elsevier Ltd. All rights reserved. Keywords: Pulsed laser deposition; Hydroxyapatite; TCP; XRD; FTIR
1. Introduction Hydroxyapatite is the main mineral component of human bone and teeth. Therefore the hydroxyapatite (HA) materials on the basis of natural and synthetic apatites are used as implants in orthopaedia and dentistry. The major applications of calcium phosphates are coatings of metallic implants because they can form real chemical bonds with surrounding bone tissue (Hench, 1991; Nelea et al., 2007). The deposition of calcium phosphates films on medical implants enable to combine the high mechanical strength of metallic implant with excellent bioactivity of the calcium phosphates surface layers. Therefore it is important to obtain the calcium phosphate coatings characterized by the proper chemical composition and physical characteristics. Calcium phosphate materials can be combined with magnesium in order to improve crystallization of phosphate deposits and therefore improve its persistence and biocompatibility (Okazaki, 1991). Among many techniques pulsed laser deposition (PLD) is commonly used for producing calcium phosphate coatings (Chrisey and
* Corresponding author. Fax: +48 22 666 89 50. E-mail address: [email protected] (M. Jedyn´ski). 0968-4328/$ – see front matter # 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.micron.2008.01.016
Hubler, 1994; Cleries et al., 2000). This method is characterized by high deposition rate as well as possibility of precise controlling of thickness and composition of a growing layer. The physical and chemical properties of deposited layers can be controlled by changing conditions of PLD process. The basic parameters of the above method are pressure of ambient gas, laser fluence, substrate temperature, wavelength and repetition of laser pulses (Mro´z, 2006; Jelinek et al., 1995). The aim of this paper was to determine the influence of presence of magnesium in the ablated target on chemical properties of deposited layer. 2. Experiment Three calcium phosphate-based materials were deposited by means of pulsed excimer ArF laser operating at 193 nm with pulse repetition of 50 Hz. The laser pulse width was 20 ns, the laser fluence was 7 J/cm2 with pulse energy of 250 mJ. The deposition time was 35 min thus the thickness of obtained films was approximately 3 mm what prevented the influence of substrate material on the physical properties of deposited layers. Three calcium phosphate pellets were used as a targets, i.e. hydroxyapatite, hydroxyapatite doped with magnesium and
W. Mro´z et al. / Micron 40 (2009) 140–142
tricalcium phosphate. All targets were made by pressing powders obtained by wet method described in S´lo´sarczyk et al. (1996). The targets were placed in central part of vacuum chamber and the laser beam was focused of 408 out of the normal surface of the target. The distance between target and substrate was 4 cm. All layers were deposited on Ti6Al4V titanium alloy substrate with TiN buffer layer. Substrates were maintained at elevated temperature of 600 50 8C. The deposition process was carried out in air atmosphere which pressure was 35 Pa.
141
second region ranged between 900 cm 1 and 1200 cm 1. The peaks in this region depict stretching modes of PO4 vibration. The peak at 480 cm 1 is visible in the case of HA and Mg-doped HA layers (Fig. 1b and c). The peak around 560 cm 1 is visible only in the spectrum of deposited tricalcium phosphate (TCP) (Fig. 1a) and the peak at 610 cm 1 is not visible. This is caused by different chemical and structural composition of the above
3. Results and discussion Fig. 1 depicts the absorption spectra (FTIR) of coatings obtained from three different calcium phosphates targets. The bands corresponding to PO4 group consist of two main regions. The first one is characterized by three peaks at 480 cm 1, 560 cm 1 and 610 cm 1 which reflect a bending mode. The
Fig. 1. Fourier spectra of deposited different calcium phosphate layers: (a) TCP, (b) HA and (c) Mg-doped HA.
Fig. 2. X-ray diffraction patterns of coatings obtained from: (a) TCP, (b) HA and (c) Mg-doped HA targets (‘‘s’’ denotes Ti6Al4V titanium alloy substrate).
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coatings. Although this peak is present in spectra of HA and Mgdoped HA but in the second case broadening of this peak is visible. The second region of PO4 mode in the TCP spectrum has only one narrow peak about 1010 cm 1. In the case of HA and Mg-doped HA this region consists of three peaks which are broadened and shifted towards higher wavenumber. This difference may be caused by different spatial stress distribution in the studied materials. The spectra of all obtained layers reveal peaks at 1360 cm 1, 1410 cm 1, 1460 cm 1 which are attributed to CO3 stretching modes. The peak at 870 cm 1 is visible in the spectra of HA and Mg-doped HA but is not present in the case of TCP. The peaks at 2860 cm 1 and 2940 cm 1 originates from stretching modes of CH molecules. The presence of CO3 as well as CH groups in deposited layers can be explained by the chemical reaction of synthesized HA and TCP powders with CO2 and H2O molecules from atmosphere. In the spectra of the all obtained layers a peak at 1620 cm 1 and the broad band in the region of 3300–3700 cm 1 are visible. The peak at 1620 cm 1 is attributed to the bending mode of OH from water molecules absorbed by the layers. The broad band around 3500 cm 1 is characterized by the stretching mode of OH coming from absorbed H2O as well as hydroxyl groups present in hydroxyapatite structure. These bands are of visibly smaller intensity in the case of Mg-doped HA than in the other coatings (Fig. 1c). In our opinion it is caused by the fact that deposited TCP and HA layers are characterized by the higroscopic structure therefore they are able to absorb more water vapour than Mg-doped HA coatings. X-ray diffraction analyses have shown the differences of polycrystalline structure of deposited layers (Fig. 2). In the case of the coating obtained from TCP target (Fig. 2a), one observes narrow peaks typical of crystalline HA and TCP and a broad peak around 308 typical of an amorphous phase. This peak in the case of HA coating (Fig. 2b) is narrower thus one can conclude that this layer containes greater amount of polycrystalline phase. The X-ray diffraction pattern of the coating obtained using Mg-doped HA target exhibits only crystalline phase of material. In this case the visible peaks attributed to HA are very narrow.
4. Summary The influence of magnesium in hydroxyapatite material on crystallinity of pulsed laser deposited layer was presented. Three calcium phosphate materials were used as a targets to deposit different coatings. HA, TCP and Mg-doped HA were used in order to determine influence of chemical structure of material on deposited layer. X-ray diffraction patterns revealed that obtained TCP as well as HA layers are of more amorphous character than Mg-doped layer. Mg-doped HA layer had polycrystalline structure. The FTIR spectrum of Mg-doped coating showed that it absorbed smaller amount of water in comparison with coatings without doped Mg. The experiment reveal that the addition of magnesium into hydroxyapatite material improve crystallinity of deposited layer.
References Chrisey, D.B., Hubler, G.K., 1994. Pulsed Laser Deposition of Thin Films. New York. Cleries, L., Martinez, E., Fernandez, J.M., Sardin, G., Esteve, J., Morenza, J.L., 2000. Mechanical properties of calcium phosphate coatings deposited by laser ablation. Biomaterials 21, 967–971. Hench, L.L., 1991. Bioceramics: from concept to clinics. J. Am. Ceram. Soc. 74, 1487–1510. Jelinek, M., Olsan, V., Jastrabik, L., Studnicka, V., Hnatowicz, V., Kvitek, J., Havranek, V., Dostalova, T., Zergioti, I., Petrakis, A., Hontzopoulos, E., Fotakis, C., 1995. Effect of processing parameters on the properties of hydroxyalapatite films grown by pulsed laser deposition. Thin Solid Films 257, 125–129. Mro´z, W., 2006. Physics of deposition of hydroxyapatite layers by pulse laser deposition method. In: Kassing, R., Petkov, P., Kulisch, W., Popov, C. (Eds.), Functional Properties of Nanostructured Materials, vol. 223. NATO Science Series II Mathematics, Physics and Chemistry. Nelea, V., Mihailescu, I.N., Jelinek, M., 2007. Pulsed laser deposition of thin films. In: Eason, R. (Ed.), Applications-led Growth of Functional Materials. Wiley–Interscience, pp. 421–456. Okazaki, M., 1991. Crystallographic bahaviour of fluoridated hydroxyapatite containing Mg2+ and CO32 ions. Biomaterials 12, 831–835. ´Slo´sarczyk, A., Stobierska, E., Paszkiewicz, Z., Gawlicki, M., 1996. Calcium phosphate materials prepared from precipitates with various calcium:phosphorus molar ratios. J. Am. Ceram. Soc. 79 (10), 2539–2544.
Micron 40 (2009) 140–142 www.elsevier.com/locate/micron
Characterization of calcium phosphate coatings doped with Mg, deposited by pulsed laser deposition technique using ArF excimer laser W. Mro´z a, M. Jedyn´ski a,*, A. Prokopiuk a, A. S´lo´sarczyk b, Z. Paszkiewicz b b
a Institute of Optoelectronics, Military University of Technology, Kaliskiego 2, 01-489 Warsaw, Poland AGH-Faculty of Material Science and Ceramics, University of Science and Technology, Al. Mickiewicza 30, 30-059 Krakow, Poland
Received 25 October 2007; received in revised form 18 January 2008; accepted 21 January 2008
Abstract Calcium phosphate layers were deposited on Ti6Al4V substrates with TiN buffer layers by use of pulsed laser deposition method. With this technique three pressed pellets consisted of tricalcium phosphate (TCP, Ca3(PO4)2), hydroxyapatite (HA, Ca10(PO4)6(OH)2) and hydroxyapatitedoped with magnesium (HA with 4% of Mg and trace amount of (Ca,Mg)3(PO4)2) were ablated using ArF excimer laser (l = 193 nm). The using of different targets enabled to determine the influence of target composition on the nature of deposited layers. The obtained deposits were characterized by means of Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction method (XRD). The obtained Fourier spectras revealed differences in terms of intensity of spectral bands of different layers. The analysis from XRD showed that Mg-doped HA layer has crystalline structure and TCP and HA layers composition is characterized by amorphous nature. # 2008 Elsevier Ltd. All rights reserved. Keywords: Pulsed laser deposition; Hydroxyapatite; TCP; XRD; FTIR
1. Introduction Hydroxyapatite is the main mineral component of human bone and teeth. Therefore the hydroxyapatite (HA) materials on the basis of natural and synthetic apatites are used as implants in orthopaedia and dentistry. The major applications of calcium phosphates are coatings of metallic implants because they can form real chemical bonds with surrounding bone tissue (Hench, 1991; Nelea et al., 2007). The deposition of calcium phosphates films on medical implants enable to combine the high mechanical strength of metallic implant with excellent bioactivity of the calcium phosphates surface layers. Therefore it is important to obtain the calcium phosphate coatings characterized by the proper chemical composition and physical characteristics. Calcium phosphate materials can be combined with magnesium in order to improve crystallization of phosphate deposits and therefore improve its persistence and biocompatibility (Okazaki, 1991). Among many techniques pulsed laser deposition (PLD) is commonly used for producing calcium phosphate coatings (Chrisey and
* Corresponding author. Fax: +48 22 666 89 50. E-mail address: [email protected] (M. Jedyn´ski). 0968-4328/$ – see front matter # 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.micron.2008.01.016
Hubler, 1994; Cleries et al., 2000). This method is characterized by high deposition rate as well as possibility of precise controlling of thickness and composition of a growing layer. The physical and chemical properties of deposited layers can be controlled by changing conditions of PLD process. The basic parameters of the above method are pressure of ambient gas, laser fluence, substrate temperature, wavelength and repetition of laser pulses (Mro´z, 2006; Jelinek et al., 1995). The aim of this paper was to determine the influence of presence of magnesium in the ablated target on chemical properties of deposited layer. 2. Experiment Three calcium phosphate-based materials were deposited by means of pulsed excimer ArF laser operating at 193 nm with pulse repetition of 50 Hz. The laser pulse width was 20 ns, the laser fluence was 7 J/cm2 with pulse energy of 250 mJ. The deposition time was 35 min thus the thickness of obtained films was approximately 3 mm what prevented the influence of substrate material on the physical properties of deposited layers. Three calcium phosphate pellets were used as a targets, i.e. hydroxyapatite, hydroxyapatite doped with magnesium and
W. Mro´z et al. / Micron 40 (2009) 140–142
tricalcium phosphate. All targets were made by pressing powders obtained by wet method described in S´lo´sarczyk et al. (1996). The targets were placed in central part of vacuum chamber and the laser beam was focused of 408 out of the normal surface of the target. The distance between target and substrate was 4 cm. All layers were deposited on Ti6Al4V titanium alloy substrate with TiN buffer layer. Substrates were maintained at elevated temperature of 600 50 8C. The deposition process was carried out in air atmosphere which pressure was 35 Pa.
141
second region ranged between 900 cm 1 and 1200 cm 1. The peaks in this region depict stretching modes of PO4 vibration. The peak at 480 cm 1 is visible in the case of HA and Mg-doped HA layers (Fig. 1b and c). The peak around 560 cm 1 is visible only in the spectrum of deposited tricalcium phosphate (TCP) (Fig. 1a) and the peak at 610 cm 1 is not visible. This is caused by different chemical and structural composition of the above
3. Results and discussion Fig. 1 depicts the absorption spectra (FTIR) of coatings obtained from three different calcium phosphates targets. The bands corresponding to PO4 group consist of two main regions. The first one is characterized by three peaks at 480 cm 1, 560 cm 1 and 610 cm 1 which reflect a bending mode. The
Fig. 1. Fourier spectra of deposited different calcium phosphate layers: (a) TCP, (b) HA and (c) Mg-doped HA.
Fig. 2. X-ray diffraction patterns of coatings obtained from: (a) TCP, (b) HA and (c) Mg-doped HA targets (‘‘s’’ denotes Ti6Al4V titanium alloy substrate).
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coatings. Although this peak is present in spectra of HA and Mgdoped HA but in the second case broadening of this peak is visible. The second region of PO4 mode in the TCP spectrum has only one narrow peak about 1010 cm 1. In the case of HA and Mg-doped HA this region consists of three peaks which are broadened and shifted towards higher wavenumber. This difference may be caused by different spatial stress distribution in the studied materials. The spectra of all obtained layers reveal peaks at 1360 cm 1, 1410 cm 1, 1460 cm 1 which are attributed to CO3 stretching modes. The peak at 870 cm 1 is visible in the spectra of HA and Mg-doped HA but is not present in the case of TCP. The peaks at 2860 cm 1 and 2940 cm 1 originates from stretching modes of CH molecules. The presence of CO3 as well as CH groups in deposited layers can be explained by the chemical reaction of synthesized HA and TCP powders with CO2 and H2O molecules from atmosphere. In the spectra of the all obtained layers a peak at 1620 cm 1 and the broad band in the region of 3300–3700 cm 1 are visible. The peak at 1620 cm 1 is attributed to the bending mode of OH from water molecules absorbed by the layers. The broad band around 3500 cm 1 is characterized by the stretching mode of OH coming from absorbed H2O as well as hydroxyl groups present in hydroxyapatite structure. These bands are of visibly smaller intensity in the case of Mg-doped HA than in the other coatings (Fig. 1c). In our opinion it is caused by the fact that deposited TCP and HA layers are characterized by the higroscopic structure therefore they are able to absorb more water vapour than Mg-doped HA coatings. X-ray diffraction analyses have shown the differences of polycrystalline structure of deposited layers (Fig. 2). In the case of the coating obtained from TCP target (Fig. 2a), one observes narrow peaks typical of crystalline HA and TCP and a broad peak around 308 typical of an amorphous phase. This peak in the case of HA coating (Fig. 2b) is narrower thus one can conclude that this layer containes greater amount of polycrystalline phase. The X-ray diffraction pattern of the coating obtained using Mg-doped HA target exhibits only crystalline phase of material. In this case the visible peaks attributed to HA are very narrow.
4. Summary The influence of magnesium in hydroxyapatite material on crystallinity of pulsed laser deposited layer was presented. Three calcium phosphate materials were used as a targets to deposit different coatings. HA, TCP and Mg-doped HA were used in order to determine influence of chemical structure of material on deposited layer. X-ray diffraction patterns revealed that obtained TCP as well as HA layers are of more amorphous character than Mg-doped layer. Mg-doped HA layer had polycrystalline structure. The FTIR spectrum of Mg-doped coating showed that it absorbed smaller amount of water in comparison with coatings without doped Mg. The experiment reveal that the addition of magnesium into hydroxyapatite material improve crystallinity of deposited layer.
References Chrisey, D.B., Hubler, G.K., 1994. Pulsed Laser Deposition of Thin Films. New York. Cleries, L., Martinez, E., Fernandez, J.M., Sardin, G., Esteve, J., Morenza, J.L., 2000. Mechanical properties of calcium phosphate coatings deposited by laser ablation. Biomaterials 21, 967–971. Hench, L.L., 1991. Bioceramics: from concept to clinics. J. Am. Ceram. Soc. 74, 1487–1510. Jelinek, M., Olsan, V., Jastrabik, L., Studnicka, V., Hnatowicz, V., Kvitek, J., Havranek, V., Dostalova, T., Zergioti, I., Petrakis, A., Hontzopoulos, E., Fotakis, C., 1995. Effect of processing parameters on the properties of hydroxyalapatite films grown by pulsed laser deposition. Thin Solid Films 257, 125–129. Mro´z, W., 2006. Physics of deposition of hydroxyapatite layers by pulse laser deposition method. In: Kassing, R., Petkov, P., Kulisch, W., Popov, C. (Eds.), Functional Properties of Nanostructured Materials, vol. 223. NATO Science Series II Mathematics, Physics and Chemistry. Nelea, V., Mihailescu, I.N., Jelinek, M., 2007. Pulsed laser deposition of thin films. In: Eason, R. (Ed.), Applications-led Growth of Functional Materials. Wiley–Interscience, pp. 421–456. Okazaki, M., 1991. Crystallographic bahaviour of fluoridated hydroxyapatite containing Mg2+ and CO32 ions. Biomaterials 12, 831–835. ´Slo´sarczyk, A., Stobierska, E., Paszkiewicz, Z., Gawlicki, M., 1996. Calcium phosphate materials prepared from precipitates with various calcium:phosphorus molar ratios. J. Am. Ceram. Soc. 79 (10), 2539–2544.