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Mechanochemical route for sulphide nanoparticles preparation
Materials Letters 57 (2003) 1585 – 1589 www.elsevier.com/locate/matlet
Mechanochemical route for sulphide nanoparticles preparation P. Bala´zˇ a,*, E. Boldizˇa´rova´ a, E. Godocˇ´ıkova´ a, J. Briancˇin b b
a Institute of Geotechnics, Slovak Academy of Sciences, Watsonova 45, 043 53 Kosˇice, Slovakia Institute of Material Research, Slovak Academy of Sciences, Watsonova 47, 043 57 Kosˇice, Slovakia
Received 25 April 2002; accepted 15 July 2002
Abstract Well-crystallized ZnS, CdS and PbS nanoparticles were successfully synthesized by the mechanochemical route from the corresponding acetates and Na2S. X-ray powder diffraction and scanning electron microscopy were used to characterize the asobtained products. The SEM measurements show the aggregates of small nanocrystals in which particle sizes of 5 – 18 nm were estimated by Scherrer’s formula. Simple flow chart of the preparation of sulphide nanoparticles was presented. D 2002 Elsevier Science B.V. All rights reserved. Keywords: Mechanochemical route; Sulphide nanoparticles; Scherrer’s formula
1. Introduction Nanoparticles of sulphides have been synthesized recently by different chemical routes with the aim to prepare materials with controlled particle morphology and size distribution [1– 12]. The routes of synthesis described in most of these papers have applied the solvothermal synthesis with the intervention of microwave, sonochemical and autoclave techniques. The diverse possibilities of mechanochemical processing for new materials preparation have been reviewed in papers [13 – 15]. In this type of processing, the chemical reactions and phase transformations take place because of the application of mechanical energy. As a consequence, reactions which normally require high temperature will occur at low temperature without any externally applied heat. Mechanochemi*
Corresponding author. Tel.: +42-1-55-6330790; fax: +42-155-6323402. E-mail address: [email protected] (P. Bala´zˇ).
cal processing belongs among the routes which can effectively control and regulate the course of solid state reactions [16]. Recent developments in mechanochemical nanoparticle synthesis have shown that nanocrystalline powder could be further processed and separate nanoparticles of the desired phase as small as 5 nm could be obtained [17 – 19]. In previous 10 years, many sulphides were synthesized directly from elemental metal and sulphur by mechanochemical processing [20 –38]. The new strategy of mechanochemical synthesis of sulphide nanoparticles will be verified in the present paper. The aim is to study the solid – solid reactions of type ðCH3 COOÞ2 Me þ Na2 S ! MeS þ 2CH3 COONa ðMe ¼ Zn; Cd; PbÞ
ð1Þ
where after finalizing reaction (1), the solid metal nanoparticles can be directly obtained by washing the unreacted precursors and soluble product.
0167-577X/02/$ - see front matter D 2002 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 7 - 5 7 7 X ( 0 2 ) 0 1 0 3 7 - 6
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P. Bala´zˇ et al. / Materials Letters 57 (2003) 1585–1589
2. Experimental The stoichiometric mixtures of Zn, Pb and Cd acetates and natrium sulphide were milled in a mill Pulverisette 6 (Germany) in order to prepare 3 g of corresponding sulphides after Eq. (1). The following conditions were used: ball charge 50 balls of 10-mm diameter, ball and vial material tungsten carbide, 10min milling time in argon atmosphere, rotational speed of the planet carrier 500 min 1. The whole flow chart of the synthesis process is given in Fig. 1. The simple procedure of the nanoparticles generation (the milling step) and their separation and cleaning (the washing, decantation and drying steps) form the whole mechanochemical route of the sulphide nanoparticles preparation. X-ray diffraction measurements were carried out using a diffractometer Dron 2.0 (Russia) with goniometer Gur 5 and FeKa radiation. The XRD lines
were identified by comparing the measured patterns to the JCPDS data cards. The grain size of MeS nanopowders (Me = Zn, Pb, Cd) were calculated from the Scherrer formula [39] as follows D¼
Krk bcosH
ð2Þ
where D—the average crystallite size, K—the shape factor, r—the radius of goniometer, k—the X-ray wavelength, b—the angular line width of half-maximum intensity and H—the Bragg’s angle. Scanning electron micrographs of the investigated samples were obtained on a scanning electron microscope BS 300 (Czech Republic).
3. Results and discussion 3.1. Zinc sulphide ZnS in Fig. 2 shows the X-ray diffraction pattern of the product after mechanochemical reaction of (CH3COO)2Zn2H2O with Na2S9H2O and postreaction washing. XRD analysis confirmed the presence of a-ZnS (JCPDS 5-0492) and sphalerite h-ZnS (JCPDS 5-566) as the only products. Mechanochemical transformation of wurtzite to cubic sphalerite is a consequence of the motion of dislocations in activated solid state [40,41]. The value of 5 nm was calculated by formula (2) for (111) plane of sphalerite h-ZnS nanoparticles. The scanning electron micrograph attached to Fig. 2 is composed of the clusters of secondary sulphide particles-agglomerates (the same SEM pictures can be identified for CdS and PbS nanoparticles in Figs. 3 and 4, respectively). 3.2. Cadmium sulphide
Fig. 1. Flow chart of the preparation of MeS nanoparticles.
X-ray diffraction pattern of the washed product of the mechanochemical reaction of (CH3COO)2Cd 2H2O with Na2S9H2O is given in Fig. 3 together with the scanning electron micrograph. Hexagonal a-CdS greenockite (JCPDS 41-1049) together with cubic hawleyite h-CdS (JCPDS 10-454) are present among the products of mechanochemical synthesis. The value of 5 nm was calculated for (111) plane of hawleyite h-
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Fig. 2. XRD pattern and SEM of the mechanochemically synthesized ZnS nanoparticles (JCPDS 5-566: sphalerite h-ZnS, JCPDS 5-0492: wurtzite a-ZnS).
Fig. 3. XRD pattern and SEM of the mechanochemically synthesized CdS nanoparticles (JCPDS 6-0313: a-greenockite, JCPDS 10-454: hawleyite h-CdS).
P. Bala´zˇ et al. / Materials Letters 57 (2003) 1585–1589
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Fig. 4. XRD pattern and SEM of the mechanochemically synthesized PbS nanoparticles (JCPDS 5-592: galena PbS).
CdS nanoparticles. The polymorphous transformations of cadmium sulphides during mechanochemical processing were investigated in papers [42,43]. The milling of hexagonal CdS phase brings about its transformation into disordered cubic CdS phase. The rate of this transformation is dependent on the method of preparation of CdS subjected to mechanochemical transformation.
4. Conclusions The simple, one-step process for crystalline ZnS, CdS and PbS nanoparticles synthesis has been presented by the application of the mechanochemical processing route. The obtained nanoparticles (5– 18 nm size) were synthesized at laboratory temperature, atmospheric pressure and at a very short reaction time without the intervention of any solvent.
3.3. Lead sulphide XRD pattern of PbS nanoparticles after the mechanochemical reaction of (CH3COO)2Pb3H2O with Na2S9H2O and subsequent processing is given in Fig. 1. We clearly see the diffraction peaks corresponding to (111), (200), (220), (311), (222), (400) and (420) planes of galena PbS phase (JCPDS 5-592). No other products were confirmed in this wellcrystallized product with the calculated particle size of crystallites of 18 nm. The same size was estimated for PbS particles prepared by gas condensation method in other paper [1].
Acknowledgements The authors would like to thank Mrs. M. Galdova´ for technical assistance. The support through the Slovak Grant Agency VEGA (grant 2/2103/22) is gratefully acknowledged.
References [1] R. Houbertz, W. Krauss, R. Birringer, U. Hartmann, Nanostruct. Mater. 9 (1997) 339.
P. Bala´zˇ et al. / Materials Letters 57 (2003) 1585–1589 [2] S.H. Yu, Y.S. Wu, J. Yang, Z.H. Han, Y. Xie, Y.T. Qian, X.M. Lin, Chem. Mater. 10 (1998) 2309. [3] Y.D. Li, H.W. Liao, Y. Ding, Y.T. Qian, L. Yang, G.E. Zhou, Chem. Mater. 10 (1998) 2301. [4] Q. Lu, J. Hu, J.K. Tang, Y. Qian, X. Lin, G. Zhou, J. Solid State Chem. 146 (1999) 484. [5] L.P. Wang, G.Y. Hong, Mater. Res. Bull. 35 (2000) 695. [6] W.X. Zhang, L. Zhang, Y.W. Cheng, Z. Hui, X.M. Zhang, Y. Xie, Y.T. Qian, Mater. Res. Bull. 35 (2000) 2009. [7] J. Zhu, S.W. Liu, O. Palchik, Y. Koltypin, A. Gedanken, J. Solid State Chem. 153 (2000) 342. [8] W.Z. Wang, Y.K. Lin, Y.J. Zhan, Ch.L. Zheng, G.G. Wang, Mater. Res. Bull. 36 (2001) 1977. [9] A.V. Murugan, R.S. Sonawe, B.B. Kale, S.K. Apte, A.V. Kulkarni, Mater. Chem. Phys. 71 (2001) 98. [10] X.H. Liao, J.J. Zhu, H.Y. Chen, Mater. Sci. Eng. B85 (2001) 85. [11] M. Chen, Y. Xie, Z. Yao, Y.T. Qian, G. Zhou, Mater. Res. Bull. 37 (2002) 247. [12] M. Chen, Y. Xie, Z.Y. Yao, Y.M. Lin, Y.T. Qian, Mater. Chem. Phys. 74 (2002) 109. [13] P.G. McCormick, Mater. Trans., JIM 36 (1995) 161. [14] E. Ivanov, C. Suryanarayana, J. Mater. Synth. Process. 8 (2000) 235. [15] C. Suraynarayana, Prog. Mater. Sci. 40 (2001) 1. [16] P. Bala´zˇ, Extractive Metallurgy of Activated Minerals, Elsevier, Amsterdam, 2000. [17] J. Ding, T. Tsuzuki, P.G. McCormick, J. Mater. Sci. 34 (1999) 5293. [18] P.G. McCormick, T. Tsuzuki, J.S. Robinson, J. Ding, Adv. Mater. 13 (2001) 1008. [19] P.G. McCormick, T. Tsuzuki, Mat. Sci. Forum 386 – 388 (2002) 377. [20] P. Matteazzi, G. Le Cae¨r, Mater. Sci. Eng. A156 (1992) 229. [21] T. Kosmac, D. Maurice, T.H. Courtney, J. Am. Ceram. Soc. 76 (1993) 2345. [22] T. Ohtani, M. Motoki, K. Koh, K. Ohsima, Mater. Res. Bull. 30 (1995) 1495.
1589
[23] T. Ohtani, K. Maruyama, K. Ohsima, Mater. Res. Bull. 32 (1997) 343. [24] T. Ohtani, A. Tsubota, K. Ohsima, Mater. Res. Bull. 34 (1999) 1143. [25] L. Takacs, M.A. Susol, J. Solid State Chem. 121 (1996) 394. [26] L. Takacs, Mat. Sci. Forum 269 – 272 (1998) 513. [27] L. Takacs, Hyperfine Interact. 111 (1998) 245. [28] T. Tsuzuki, J. Ding, P.G. McCormick, Physica B 239 (1997) 378. [29] T. Tsuzuki, P.G. McCormick, Appl. Phys. A 65 (1997) 607. [30] T. Tsuzuki, P.G. McCormick, Nanostruct. Mater. 12 (1999) 75. [31] R. Lin, J.Z. Jiang, R.K. Larsen, S. Morup, F.J. Berry, Hyperfine Interact. C 3 (1998) 45. [32] J.Z. Jiang, R.K. Larsen, R. Lin, S. Morup, I. Chorkendorff, K. Nielsen, K. Hansen, K. West, J. Solid State Chem. 138 (1998) 114. [33] P. Bala´zˇ, T. Havlı´k, J. Lipka, R. Kammel, Scripta Metall. Mater. 32 (1995) 1357. [34] P. Bala´zˇ, Z. Bastl, T. Havlı´k, J. Lipka, I. To´th, Mat. Sci. Forum 235 – 238 (1997) 217. [35] P. Bala´zˇ, T. Ohtani, Z. Bastl, E. Boldizˇa´rova´, J. Solid State Chem. 144 (1999) 1. [36] P. Bala´zˇ, L. Takacs, J.Z. Jiang, V. Soika, M. Luxova´, Mat. Sci. Forum 386 – 388 (2002) 257. [37] P. Bala´zˇ, L. Takacs, T. Ohtani, D.E. Mack, E. Boldizˇa´rova´, V. Soika, M. Achimovicˇova´, J. Alloys Compd. 337 (2002) 76. [38] R. Blachnik, A. Mu¨ller, Thermochim. Acta 361 (2000) 31. [39] H.P. Klugg, L.E. Alexander, X-Ray Diffraction Procedures, Wiley, New York, 1954. [40] E.G. Avvakumov, Mechanical Methods of Chemical Processes Activation, Nauka, Novosibirsk, 1979. [41] M. Senna, Cryst. Res. Technol. 20 (1985) 209. [42] G. Ohtani, M. Senna, Thermochim. Acta. 60 (1983) 125. [43] G.J. Durose, A.T. Fellows, A.W. Brinkman, G.J. Russel, J. Mater. Sci. 20 (1985) 3783.
Mechanochemical route for sulphide nanoparticles preparation P. Bala´zˇ a,*, E. Boldizˇa´rova´ a, E. Godocˇ´ıkova´ a, J. Briancˇin b b
a Institute of Geotechnics, Slovak Academy of Sciences, Watsonova 45, 043 53 Kosˇice, Slovakia Institute of Material Research, Slovak Academy of Sciences, Watsonova 47, 043 57 Kosˇice, Slovakia
Received 25 April 2002; accepted 15 July 2002
Abstract Well-crystallized ZnS, CdS and PbS nanoparticles were successfully synthesized by the mechanochemical route from the corresponding acetates and Na2S. X-ray powder diffraction and scanning electron microscopy were used to characterize the asobtained products. The SEM measurements show the aggregates of small nanocrystals in which particle sizes of 5 – 18 nm were estimated by Scherrer’s formula. Simple flow chart of the preparation of sulphide nanoparticles was presented. D 2002 Elsevier Science B.V. All rights reserved. Keywords: Mechanochemical route; Sulphide nanoparticles; Scherrer’s formula
1. Introduction Nanoparticles of sulphides have been synthesized recently by different chemical routes with the aim to prepare materials with controlled particle morphology and size distribution [1– 12]. The routes of synthesis described in most of these papers have applied the solvothermal synthesis with the intervention of microwave, sonochemical and autoclave techniques. The diverse possibilities of mechanochemical processing for new materials preparation have been reviewed in papers [13 – 15]. In this type of processing, the chemical reactions and phase transformations take place because of the application of mechanical energy. As a consequence, reactions which normally require high temperature will occur at low temperature without any externally applied heat. Mechanochemi*
Corresponding author. Tel.: +42-1-55-6330790; fax: +42-155-6323402. E-mail address: [email protected] (P. Bala´zˇ).
cal processing belongs among the routes which can effectively control and regulate the course of solid state reactions [16]. Recent developments in mechanochemical nanoparticle synthesis have shown that nanocrystalline powder could be further processed and separate nanoparticles of the desired phase as small as 5 nm could be obtained [17 – 19]. In previous 10 years, many sulphides were synthesized directly from elemental metal and sulphur by mechanochemical processing [20 –38]. The new strategy of mechanochemical synthesis of sulphide nanoparticles will be verified in the present paper. The aim is to study the solid – solid reactions of type ðCH3 COOÞ2 Me þ Na2 S ! MeS þ 2CH3 COONa ðMe ¼ Zn; Cd; PbÞ
ð1Þ
where after finalizing reaction (1), the solid metal nanoparticles can be directly obtained by washing the unreacted precursors and soluble product.
0167-577X/02/$ - see front matter D 2002 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 7 - 5 7 7 X ( 0 2 ) 0 1 0 3 7 - 6
1586
P. Bala´zˇ et al. / Materials Letters 57 (2003) 1585–1589
2. Experimental The stoichiometric mixtures of Zn, Pb and Cd acetates and natrium sulphide were milled in a mill Pulverisette 6 (Germany) in order to prepare 3 g of corresponding sulphides after Eq. (1). The following conditions were used: ball charge 50 balls of 10-mm diameter, ball and vial material tungsten carbide, 10min milling time in argon atmosphere, rotational speed of the planet carrier 500 min 1. The whole flow chart of the synthesis process is given in Fig. 1. The simple procedure of the nanoparticles generation (the milling step) and their separation and cleaning (the washing, decantation and drying steps) form the whole mechanochemical route of the sulphide nanoparticles preparation. X-ray diffraction measurements were carried out using a diffractometer Dron 2.0 (Russia) with goniometer Gur 5 and FeKa radiation. The XRD lines
were identified by comparing the measured patterns to the JCPDS data cards. The grain size of MeS nanopowders (Me = Zn, Pb, Cd) were calculated from the Scherrer formula [39] as follows D¼
Krk bcosH
ð2Þ
where D—the average crystallite size, K—the shape factor, r—the radius of goniometer, k—the X-ray wavelength, b—the angular line width of half-maximum intensity and H—the Bragg’s angle. Scanning electron micrographs of the investigated samples were obtained on a scanning electron microscope BS 300 (Czech Republic).
3. Results and discussion 3.1. Zinc sulphide ZnS in Fig. 2 shows the X-ray diffraction pattern of the product after mechanochemical reaction of (CH3COO)2Zn2H2O with Na2S9H2O and postreaction washing. XRD analysis confirmed the presence of a-ZnS (JCPDS 5-0492) and sphalerite h-ZnS (JCPDS 5-566) as the only products. Mechanochemical transformation of wurtzite to cubic sphalerite is a consequence of the motion of dislocations in activated solid state [40,41]. The value of 5 nm was calculated by formula (2) for (111) plane of sphalerite h-ZnS nanoparticles. The scanning electron micrograph attached to Fig. 2 is composed of the clusters of secondary sulphide particles-agglomerates (the same SEM pictures can be identified for CdS and PbS nanoparticles in Figs. 3 and 4, respectively). 3.2. Cadmium sulphide
Fig. 1. Flow chart of the preparation of MeS nanoparticles.
X-ray diffraction pattern of the washed product of the mechanochemical reaction of (CH3COO)2Cd 2H2O with Na2S9H2O is given in Fig. 3 together with the scanning electron micrograph. Hexagonal a-CdS greenockite (JCPDS 41-1049) together with cubic hawleyite h-CdS (JCPDS 10-454) are present among the products of mechanochemical synthesis. The value of 5 nm was calculated for (111) plane of hawleyite h-
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Fig. 2. XRD pattern and SEM of the mechanochemically synthesized ZnS nanoparticles (JCPDS 5-566: sphalerite h-ZnS, JCPDS 5-0492: wurtzite a-ZnS).
Fig. 3. XRD pattern and SEM of the mechanochemically synthesized CdS nanoparticles (JCPDS 6-0313: a-greenockite, JCPDS 10-454: hawleyite h-CdS).
P. Bala´zˇ et al. / Materials Letters 57 (2003) 1585–1589
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Fig. 4. XRD pattern and SEM of the mechanochemically synthesized PbS nanoparticles (JCPDS 5-592: galena PbS).
CdS nanoparticles. The polymorphous transformations of cadmium sulphides during mechanochemical processing were investigated in papers [42,43]. The milling of hexagonal CdS phase brings about its transformation into disordered cubic CdS phase. The rate of this transformation is dependent on the method of preparation of CdS subjected to mechanochemical transformation.
4. Conclusions The simple, one-step process for crystalline ZnS, CdS and PbS nanoparticles synthesis has been presented by the application of the mechanochemical processing route. The obtained nanoparticles (5– 18 nm size) were synthesized at laboratory temperature, atmospheric pressure and at a very short reaction time without the intervention of any solvent.
3.3. Lead sulphide XRD pattern of PbS nanoparticles after the mechanochemical reaction of (CH3COO)2Pb3H2O with Na2S9H2O and subsequent processing is given in Fig. 1. We clearly see the diffraction peaks corresponding to (111), (200), (220), (311), (222), (400) and (420) planes of galena PbS phase (JCPDS 5-592). No other products were confirmed in this wellcrystallized product with the calculated particle size of crystallites of 18 nm. The same size was estimated for PbS particles prepared by gas condensation method in other paper [1].
Acknowledgements The authors would like to thank Mrs. M. Galdova´ for technical assistance. The support through the Slovak Grant Agency VEGA (grant 2/2103/22) is gratefully acknowledged.
References [1] R. Houbertz, W. Krauss, R. Birringer, U. Hartmann, Nanostruct. Mater. 9 (1997) 339.
P. Bala´zˇ et al. / Materials Letters 57 (2003) 1585–1589 [2] S.H. Yu, Y.S. Wu, J. Yang, Z.H. Han, Y. Xie, Y.T. Qian, X.M. Lin, Chem. Mater. 10 (1998) 2309. [3] Y.D. Li, H.W. Liao, Y. Ding, Y.T. Qian, L. Yang, G.E. Zhou, Chem. Mater. 10 (1998) 2301. [4] Q. Lu, J. Hu, J.K. Tang, Y. Qian, X. Lin, G. Zhou, J. Solid State Chem. 146 (1999) 484. [5] L.P. Wang, G.Y. Hong, Mater. Res. Bull. 35 (2000) 695. [6] W.X. Zhang, L. Zhang, Y.W. Cheng, Z. Hui, X.M. Zhang, Y. Xie, Y.T. Qian, Mater. Res. Bull. 35 (2000) 2009. [7] J. Zhu, S.W. Liu, O. Palchik, Y. Koltypin, A. Gedanken, J. Solid State Chem. 153 (2000) 342. [8] W.Z. Wang, Y.K. Lin, Y.J. Zhan, Ch.L. Zheng, G.G. Wang, Mater. Res. Bull. 36 (2001) 1977. [9] A.V. Murugan, R.S. Sonawe, B.B. Kale, S.K. Apte, A.V. Kulkarni, Mater. Chem. Phys. 71 (2001) 98. [10] X.H. Liao, J.J. Zhu, H.Y. Chen, Mater. Sci. Eng. B85 (2001) 85. [11] M. Chen, Y. Xie, Z. Yao, Y.T. Qian, G. Zhou, Mater. Res. Bull. 37 (2002) 247. [12] M. Chen, Y. Xie, Z.Y. Yao, Y.M. Lin, Y.T. Qian, Mater. Chem. Phys. 74 (2002) 109. [13] P.G. McCormick, Mater. Trans., JIM 36 (1995) 161. [14] E. Ivanov, C. Suryanarayana, J. Mater. Synth. Process. 8 (2000) 235. [15] C. Suraynarayana, Prog. Mater. Sci. 40 (2001) 1. [16] P. Bala´zˇ, Extractive Metallurgy of Activated Minerals, Elsevier, Amsterdam, 2000. [17] J. Ding, T. Tsuzuki, P.G. McCormick, J. Mater. Sci. 34 (1999) 5293. [18] P.G. McCormick, T. Tsuzuki, J.S. Robinson, J. Ding, Adv. Mater. 13 (2001) 1008. [19] P.G. McCormick, T. Tsuzuki, Mat. Sci. Forum 386 – 388 (2002) 377. [20] P. Matteazzi, G. Le Cae¨r, Mater. Sci. Eng. A156 (1992) 229. [21] T. Kosmac, D. Maurice, T.H. Courtney, J. Am. Ceram. Soc. 76 (1993) 2345. [22] T. Ohtani, M. Motoki, K. Koh, K. Ohsima, Mater. Res. Bull. 30 (1995) 1495.
1589
[23] T. Ohtani, K. Maruyama, K. Ohsima, Mater. Res. Bull. 32 (1997) 343. [24] T. Ohtani, A. Tsubota, K. Ohsima, Mater. Res. Bull. 34 (1999) 1143. [25] L. Takacs, M.A. Susol, J. Solid State Chem. 121 (1996) 394. [26] L. Takacs, Mat. Sci. Forum 269 – 272 (1998) 513. [27] L. Takacs, Hyperfine Interact. 111 (1998) 245. [28] T. Tsuzuki, J. Ding, P.G. McCormick, Physica B 239 (1997) 378. [29] T. Tsuzuki, P.G. McCormick, Appl. Phys. A 65 (1997) 607. [30] T. Tsuzuki, P.G. McCormick, Nanostruct. Mater. 12 (1999) 75. [31] R. Lin, J.Z. Jiang, R.K. Larsen, S. Morup, F.J. Berry, Hyperfine Interact. C 3 (1998) 45. [32] J.Z. Jiang, R.K. Larsen, R. Lin, S. Morup, I. Chorkendorff, K. Nielsen, K. Hansen, K. West, J. Solid State Chem. 138 (1998) 114. [33] P. Bala´zˇ, T. Havlı´k, J. Lipka, R. Kammel, Scripta Metall. Mater. 32 (1995) 1357. [34] P. Bala´zˇ, Z. Bastl, T. Havlı´k, J. Lipka, I. To´th, Mat. Sci. Forum 235 – 238 (1997) 217. [35] P. Bala´zˇ, T. Ohtani, Z. Bastl, E. Boldizˇa´rova´, J. Solid State Chem. 144 (1999) 1. [36] P. Bala´zˇ, L. Takacs, J.Z. Jiang, V. Soika, M. Luxova´, Mat. Sci. Forum 386 – 388 (2002) 257. [37] P. Bala´zˇ, L. Takacs, T. Ohtani, D.E. Mack, E. Boldizˇa´rova´, V. Soika, M. Achimovicˇova´, J. Alloys Compd. 337 (2002) 76. [38] R. Blachnik, A. Mu¨ller, Thermochim. Acta 361 (2000) 31. [39] H.P. Klugg, L.E. Alexander, X-Ray Diffraction Procedures, Wiley, New York, 1954. [40] E.G. Avvakumov, Mechanical Methods of Chemical Processes Activation, Nauka, Novosibirsk, 1979. [41] M. Senna, Cryst. Res. Technol. 20 (1985) 209. [42] G. Ohtani, M. Senna, Thermochim. Acta. 60 (1983) 125. [43] G.J. Durose, A.T. Fellows, A.W. Brinkman, G.J. Russel, J. Mater. Sci. 20 (1985) 3783.