- Email: [email protected]
High pressure behaviour of PuBi studied by X-ray diffraction
Journal of Alloys and Compounds 284 (1999) 65–69
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High pressure behaviour of PuBi studied by X-ray diffraction ´ Y. Meresse, S. Heathman*, C. Rijkeboer, J. Rebizant European Commission, Joint Research Centre, Institute for Transuranium Elements, Postfach 2340, 76125 Karlsruhe, Germany Received 16 November 1998
Abstract High-pressure (up to 50 GPa) X-ray diffraction studies were performed on PuBi using energy dispersive techniques with nominal collection angles of 58 and 78. This compound, which exhibits a NaCl (B1) type structure at ambient pressure, undergoes a crystallographic transition to a tetragonal P4 /mmm phase at 10 GPa, which remained up to 42 GPa. A second phase transformation to a CsCl-type-structure (B2) occurred above 42 GPa. The first phase transformation is accompanied by a 12% volume collapse; a volume irregularity was not observed for the second transition. The bulk modulus (B0 561 GPa) and its pressure derivative (B 09 56.1) were calculated for PuBi from its pressure-volume relationship up to the first transition at 10 GPa. 1999 Elsevier Science S.A. All rights reserved. Keywords: PuBi; Diamond anvil cell; Actinides; High pressure
1. Introduction The 5f electrons in the actinide elements show variable behaviour, depending on the particular element, the material and the specific conditions being considered. In this regard, many studies have been carried out with actinide compounds to understand better the role of their 5f electrons during the application of pressure. One potential effect of pressure is to force atoms closer, which may promote several changes, including delocalisation of the 5f electrons. In the actinide series, Pu is considered to be the last member where the 5f electrons are involved in the metallic bonding at normal temperature and pressure. Thus, there is a special interest in compounds of Pu to determine what effect pressure may have on the 5f electrons in compounds of Pu. AnX compounds such as monocarbides, monopnictides or monochalcogenides have been the subject of many crystallographic studies [1–12]. Of these compounds, the actinide bismuthides have attracted interest for comparing their pressure dependence with that of other monopnictides and monochalcogenides. Other monobismuthides in the actinide series (UBi, NpBi, AmBi and CmBi) have been studied under pressure and also found to display high pressure phase transitions, from *Corresponding author. E-mail: [email protected]
a B1-type structure to either a B2, and / or a tetragonal structure [13–15].
2. Experimental details
2.1. Materials PuBi was obtained by levitation melting of the two elements. The materials were introduced as a pelletised powdered mixture into a water-cooled, Hukin crucible and this mixture heated using radio-frequency to 16008C under a high-purity, argon atmosphere [16]. A lattice parameter of 635.88(8) pm was determined at ambient pressure by the conventional Debye-Scherrer method and is in reasonably good agreement with the literature value of 635.0(1) [17].
2.2. High pressure studies The various steps of the experiment involving PuBi (i.e., sample loading, pressure determinations, obtaining the Xray spectrum, etc.) were carried out in a nitrogen-filled gloved box. For the high-pressure experiments, a few micrograms of the PuBi and a ruby chip were loaded into a 200 mm hole
0925-8388 / 99 / $ – see front matter 1999 Elsevier Science S.A. All rights reserved. PII: S0925-8388( 98 )00952-9
66
´ et al. / Journal of Alloys and Compounds 284 (1999) 65 – 69 Y. Meresse
of a pre-indented Inconel gasket, maintained between the diamond anvils in a Syassen-Holzapfel type pressure cell. Dried silicone oil was used as the pressure transmitting medium. Pressures at the different steps were determined by the ruby fluorescence method [18]. Energy dispersive X-ray diffraction (EDXRD) spectra
were recorded simultaneously at two Bragg angles, which allows more extensive crystallographic data to be collected for each analysis. The diffraction angles used were precisely determined by using a UC standard. The exact angles were determined to be 4.918 and 7.008. Theoretical spacings were calculated using the ENDIX
Fig. 1. Diffraction spectra of PuBi showing NaCl type (B1) to tetragonal and tetragonal to CsCl type (B2) phase transitions. (hkl, hkl, hkl: respectively indexed in the (B1), tetragonal and (B2) structures, *: Pu fluorescence lines, 앳: 241 Am gamma lines).
´ et al. / Journal of Alloys and Compounds 284 (1999) 65 – 69 Y. Meresse
program [19] and the calculation of the lattice parameters was made using a modified POWLES least squares program [20].
3. High pressure crystal structure
3.1. Experimental results The crystallographic behaviour of the sample was studied up to 50 GPa at room temperature in 42 steps of increasing pressure and ten steps of decreasing pressure. For each pressure, the lattice parameters and the relative volume V /V0 were calculated. As the pressure was increased, the sample displayed two new phases, which are represented in Fig. 1. Spectra a, b, c and d in Fig. 1 were collected at the 4.918 angle during a period of 14 h while spectrum e was acquired over a 22 h period. The 7 degree spectra, which provided diffraction to smaller inter-planar spacing, are not shown in Fig. 1 but the data are included in Fig. 2. The two angles gave comparable results for the overlapping diffraction regions. At ambient pressure Fig. 1a, PuBi exhibited the NaCltype structure with a lattice parameter determined in the
67
pressure cell as a5635.8 pm. After 8 GPa, a phase transformation was initiated (see Fig. 1b) and the transition was assigned to occur at 9.5 GPa. A large doublet appeared between the (200) and the (220) peaks of the NaCl-form and a large single peak was also observed between the (220) and the (222) of this B1 structure. These new peaks intensified as the pressure was increased, and by 13 GPa, the B1 structure had completely disappeared. Fig. 1c shows the X-ray spectrum obtained at 14.5 GPa, which corresponds to the 2nd phase, indexed as a tetragonal structure (space group P4 /mmm). The doublet (110) (101) and the two single peaks (200 and 211 peaks) belong to this tetragonal phase This phase transition is accompanied by a 12% volume decrease. Above 36 GPa, the diffraction spectrum again changed. The doublet (110, 101 peaks) became a single peak, as shown in Fig. 1d. The last spectrum Fig. 1e corresponds to the data collected at the highest pressure (50 GPa) in the study, which represents the third phase. This phase corresponds to a B2-type structure (space group Pm3m). The parasitic peaks observed in the lower energy region of the spectra (at 26–36 keV) are due to the fluorescence of Pu and the extraneous 241 Am gamma background present in the glove box. The diffraction peaks and lattice plane spacing as a
Fig. 2. Observed lattice spacing of PuBi as a function of pressure. Open circles denote the (B1) phase, filled circles denote the tetragonal phase and open diamonds refer to the (B2) phase.
´ et al. / Journal of Alloys and Compounds 284 (1999) 65 – 69 Y. Meresse
68
Fig. 3. Relative volume of PuBi as a function of pressure. (Filled circles refer to increasing pressure and open circles to decreasing pressure).
function of pressure Fig. 2, show clearly the evolution of the phase transitions, where the multiple diffraction lines of the initial phases (B1 type) and the first pressure phase (tetragonal) can be clearly indexed. In contrast, the third phase, being a CsCl-type structure, is represented by only four diffraction lines.
3.2. Bulk modulus and the equation of state The relative volume of PuBi is plotted as a function of pressure in Fig. 3. The B1-tetragonal transformation represents a first order transition and is accompanied by a 12% volume collapse, whereas a volume discontinuity was not observed for the second transition. The transition tetragonal to B2, is a simple distortion along the c axis which does not involve a significant change in the symmetry of the system. The isothermal bulk modulus (B0 ) and its pressure derivative (B 90 ) were calculated from the low pressure data (up to 10 GPa) by fitting the V /V0 data to the Birch and Murnaghan equations of state [21,22] and gave the following values. Birch equation, B0 56163.3 GPa, B 90 56.461.2 and Murnaghan equation, B0 56263.0 GPa, B 09 5 5.860.89.
structure and then a final CsCl (B2) phase is interesting when compared to the pressure behaviour of other monobismuthides. Both UBi and NpBi [15,23] transform directly from (B1) to (B2) at 5 and 8 GPa, respectively, whereas AmBi [14] transforms directly from (B1) to tetragonal at 14 GPa. CmBi [15] on the other hand, exhibits an intermediate CsCl (B2) structure at 12 GPa before its final tetragonal phase, which appears at 20 GPa. In the case of the monoantimonides NpSb [24] transforms directly from the (B1) to tetragonal at 12 GPa and PuSb [24,25] also shows an intermediate (B2) phase at 18 GPa before becoming tetragonal at 42 GPa identical to CmBi. For PuSb, it is believed that Sb–Sb bonding leads to the tetragonal structure and that the CsCl phase appears only above a certain ratio of cation to anion radii. For the higher actinides, it is probable that the transitions occur due to f–p (An f and Bi p electrons) interactions. These differences are believed to be due in part to the different An–An and An–Bi distances encountered across the series, in addition to the presence of localised and itinerant f electrons. These factors will be discussed in a forthcoming publication dealing with AmBi [14].
4. Conclusions
Acknowledgements
This present work extends previous studies performed on the pressure behaviour of actinide monobismuthides to PuBi. This actinide monobismuthide was of particular interest to explore for unusual behaviour under pressure, as Pu is the last member of the actinide series where the 5f electrons are normally delocalised in the elemental state. We have concluded that the pressure behaviour of PuBi observed up to 50 GPa is in general similar to that of other actinide monobismuthides. The appearance of both an intermediate tetragonal
YM thanks the EUROPEAN Commission for support given in the frame of the program ‘Human Capital and Mobility’.
References [1] U. Benedict, S. Dabos-Seignon, S. Heathman, J.P. Dancausse, M. Gensini, E. Gering, J.C. Spirlet, High-Pressure Phases and Compressibility of Neptunium and Plutonium Compounds. In: L.R. Morss, J.
´ et al. / Journal of Alloys and Compounds 284 (1999) 65 – 69 Y. Meresse
[2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13]
Fuger (Eds.), Transuranium Elements A Half Century, American Chemical Society, Washington DC, Chapter. 38, 1992, p. 396. U. Benedict, J. Less-Common Metals 128 (1987) 7. ´ O. L. Gerward, J. Staun Olsen, U. Benedict, S. Dabos, J.-P. Itie, Vogt, High Temp. High Press. 20 (1988) 545. J. Staun Olsen, L. Gerward, U. Benedict, H. Luo, O. Vogt, High Temp. High Press. 20 (1988) 553. L. Gerward, J. Staun Olsen, U. Benedict, S. Dabos, O. Vogt, High Pressure Res. 1 (1989) 235. ´ O. J. Staun Olsen, L. Gerward, U. Benedict, S. Dabos, J.-P. Itie, Vogt, High Pressure Res. 1 (1989) 253. ` Physica S. Dabos, C. Dufour, U. Benedict, J.-C. Spirlet, M. Pages, B. 144 (1986) 79. ´ J. LessS. Dabos Seignon, U. Benedict, J.-C. Spirlet, M. Pages, Common Met. 153 (1989) 133. S. Dabos-Seignon, U. Benedict, S. Heathman, J.-C. Spirlet, M. ´ J. Less Common Met. 160 (1990) 35. Pages, M. Gensini, E. Gering, S. Heathman, U. Benedict, J.-C. Spirlet, High Pressure Res. 2 (1990) 347. U. Benedict, J. Alloys Comp. 193 (1993) 88. U. Benedict, J. Alloys Comp. 223 (1995) 216. M. Gensini, R.G. Haire, U. Benedict, F. Hulliger, J. Rebizant, High Pressure Phases and Compressibility of the B1-Type compounds CmBi, UBi and NpSe. Annual Report of the Institute for Transuranium Elements, 1991, EUR 13815 EN, p. 157.
69
[14] S. Heathman, R.G. Haire, U. Benedict, Energy dispersive X-ray diffraction analysis of AmBi under pressure. Annual Report of the Institute for Transuranium Elements, 1994, EUR 16152 EN, p. 144. [15] M. Gensini, R.G. Haire, U. Benedict, F. Hulliger, J. Rebizant, Physica B. 190 (1993) 75. [16] J.C. Spirlet, O. Vogt, Sample preparation and crystal growth for solid state actinide research. In: Handbook on the Physics and Chemistry of the Actinides, Vol. 1, Chapter 2, 1984, p. 79. [17] JCPDS card: 41-1188. [18] H.K. Mao, P.M. Bell, J.W. Shaner, D.J. Steinberg, J. Appl. Phys. 49 (1978) 3276. [19] E. Hovestreydt, E. Parthe, U. Benedict, ENDIX Report EUR 10874 (1987), J. Appl. Cryst. 21 (1988) 282. [20] E. Williams, Report IS-1052, Ames Laboratory at Iowa State, University of Science and Technology, Ames, IA, USA, 1964. [21] F. Birch, Phys. Rev. 71 (1947) 809. [22] F.D. Murnaghan, Am. J. Math. 49 (1937) 235. [23] U. Benedict, S. Dabos-Seignon, J.P. Dancausse, M. Gensini, E. Gering, S. Heathman, H. Luo, J. Staun Olsen, L. Gerward, R.G. Haire, J. Alloys Comp. 181 (1992) 1. [24] S. Dabos-Seignon, U. Benedict, S. Heathman, J.C. Spirlet, J. LessCommon Met. 160 (1990) 35. [25] U. Benedict, S. Dabos-Seignon, H. Luo, S. Heathman, J. Nucl. Mat. 166 (1989) 48.
L
High pressure behaviour of PuBi studied by X-ray diffraction ´ Y. Meresse, S. Heathman*, C. Rijkeboer, J. Rebizant European Commission, Joint Research Centre, Institute for Transuranium Elements, Postfach 2340, 76125 Karlsruhe, Germany Received 16 November 1998
Abstract High-pressure (up to 50 GPa) X-ray diffraction studies were performed on PuBi using energy dispersive techniques with nominal collection angles of 58 and 78. This compound, which exhibits a NaCl (B1) type structure at ambient pressure, undergoes a crystallographic transition to a tetragonal P4 /mmm phase at 10 GPa, which remained up to 42 GPa. A second phase transformation to a CsCl-type-structure (B2) occurred above 42 GPa. The first phase transformation is accompanied by a 12% volume collapse; a volume irregularity was not observed for the second transition. The bulk modulus (B0 561 GPa) and its pressure derivative (B 09 56.1) were calculated for PuBi from its pressure-volume relationship up to the first transition at 10 GPa. 1999 Elsevier Science S.A. All rights reserved. Keywords: PuBi; Diamond anvil cell; Actinides; High pressure
1. Introduction The 5f electrons in the actinide elements show variable behaviour, depending on the particular element, the material and the specific conditions being considered. In this regard, many studies have been carried out with actinide compounds to understand better the role of their 5f electrons during the application of pressure. One potential effect of pressure is to force atoms closer, which may promote several changes, including delocalisation of the 5f electrons. In the actinide series, Pu is considered to be the last member where the 5f electrons are involved in the metallic bonding at normal temperature and pressure. Thus, there is a special interest in compounds of Pu to determine what effect pressure may have on the 5f electrons in compounds of Pu. AnX compounds such as monocarbides, monopnictides or monochalcogenides have been the subject of many crystallographic studies [1–12]. Of these compounds, the actinide bismuthides have attracted interest for comparing their pressure dependence with that of other monopnictides and monochalcogenides. Other monobismuthides in the actinide series (UBi, NpBi, AmBi and CmBi) have been studied under pressure and also found to display high pressure phase transitions, from *Corresponding author. E-mail: [email protected]
a B1-type structure to either a B2, and / or a tetragonal structure [13–15].
2. Experimental details
2.1. Materials PuBi was obtained by levitation melting of the two elements. The materials were introduced as a pelletised powdered mixture into a water-cooled, Hukin crucible and this mixture heated using radio-frequency to 16008C under a high-purity, argon atmosphere [16]. A lattice parameter of 635.88(8) pm was determined at ambient pressure by the conventional Debye-Scherrer method and is in reasonably good agreement with the literature value of 635.0(1) [17].
2.2. High pressure studies The various steps of the experiment involving PuBi (i.e., sample loading, pressure determinations, obtaining the Xray spectrum, etc.) were carried out in a nitrogen-filled gloved box. For the high-pressure experiments, a few micrograms of the PuBi and a ruby chip were loaded into a 200 mm hole
0925-8388 / 99 / $ – see front matter 1999 Elsevier Science S.A. All rights reserved. PII: S0925-8388( 98 )00952-9
66
´ et al. / Journal of Alloys and Compounds 284 (1999) 65 – 69 Y. Meresse
of a pre-indented Inconel gasket, maintained between the diamond anvils in a Syassen-Holzapfel type pressure cell. Dried silicone oil was used as the pressure transmitting medium. Pressures at the different steps were determined by the ruby fluorescence method [18]. Energy dispersive X-ray diffraction (EDXRD) spectra
were recorded simultaneously at two Bragg angles, which allows more extensive crystallographic data to be collected for each analysis. The diffraction angles used were precisely determined by using a UC standard. The exact angles were determined to be 4.918 and 7.008. Theoretical spacings were calculated using the ENDIX
Fig. 1. Diffraction spectra of PuBi showing NaCl type (B1) to tetragonal and tetragonal to CsCl type (B2) phase transitions. (hkl, hkl, hkl: respectively indexed in the (B1), tetragonal and (B2) structures, *: Pu fluorescence lines, 앳: 241 Am gamma lines).
´ et al. / Journal of Alloys and Compounds 284 (1999) 65 – 69 Y. Meresse
program [19] and the calculation of the lattice parameters was made using a modified POWLES least squares program [20].
3. High pressure crystal structure
3.1. Experimental results The crystallographic behaviour of the sample was studied up to 50 GPa at room temperature in 42 steps of increasing pressure and ten steps of decreasing pressure. For each pressure, the lattice parameters and the relative volume V /V0 were calculated. As the pressure was increased, the sample displayed two new phases, which are represented in Fig. 1. Spectra a, b, c and d in Fig. 1 were collected at the 4.918 angle during a period of 14 h while spectrum e was acquired over a 22 h period. The 7 degree spectra, which provided diffraction to smaller inter-planar spacing, are not shown in Fig. 1 but the data are included in Fig. 2. The two angles gave comparable results for the overlapping diffraction regions. At ambient pressure Fig. 1a, PuBi exhibited the NaCltype structure with a lattice parameter determined in the
67
pressure cell as a5635.8 pm. After 8 GPa, a phase transformation was initiated (see Fig. 1b) and the transition was assigned to occur at 9.5 GPa. A large doublet appeared between the (200) and the (220) peaks of the NaCl-form and a large single peak was also observed between the (220) and the (222) of this B1 structure. These new peaks intensified as the pressure was increased, and by 13 GPa, the B1 structure had completely disappeared. Fig. 1c shows the X-ray spectrum obtained at 14.5 GPa, which corresponds to the 2nd phase, indexed as a tetragonal structure (space group P4 /mmm). The doublet (110) (101) and the two single peaks (200 and 211 peaks) belong to this tetragonal phase This phase transition is accompanied by a 12% volume decrease. Above 36 GPa, the diffraction spectrum again changed. The doublet (110, 101 peaks) became a single peak, as shown in Fig. 1d. The last spectrum Fig. 1e corresponds to the data collected at the highest pressure (50 GPa) in the study, which represents the third phase. This phase corresponds to a B2-type structure (space group Pm3m). The parasitic peaks observed in the lower energy region of the spectra (at 26–36 keV) are due to the fluorescence of Pu and the extraneous 241 Am gamma background present in the glove box. The diffraction peaks and lattice plane spacing as a
Fig. 2. Observed lattice spacing of PuBi as a function of pressure. Open circles denote the (B1) phase, filled circles denote the tetragonal phase and open diamonds refer to the (B2) phase.
´ et al. / Journal of Alloys and Compounds 284 (1999) 65 – 69 Y. Meresse
68
Fig. 3. Relative volume of PuBi as a function of pressure. (Filled circles refer to increasing pressure and open circles to decreasing pressure).
function of pressure Fig. 2, show clearly the evolution of the phase transitions, where the multiple diffraction lines of the initial phases (B1 type) and the first pressure phase (tetragonal) can be clearly indexed. In contrast, the third phase, being a CsCl-type structure, is represented by only four diffraction lines.
3.2. Bulk modulus and the equation of state The relative volume of PuBi is plotted as a function of pressure in Fig. 3. The B1-tetragonal transformation represents a first order transition and is accompanied by a 12% volume collapse, whereas a volume discontinuity was not observed for the second transition. The transition tetragonal to B2, is a simple distortion along the c axis which does not involve a significant change in the symmetry of the system. The isothermal bulk modulus (B0 ) and its pressure derivative (B 90 ) were calculated from the low pressure data (up to 10 GPa) by fitting the V /V0 data to the Birch and Murnaghan equations of state [21,22] and gave the following values. Birch equation, B0 56163.3 GPa, B 90 56.461.2 and Murnaghan equation, B0 56263.0 GPa, B 09 5 5.860.89.
structure and then a final CsCl (B2) phase is interesting when compared to the pressure behaviour of other monobismuthides. Both UBi and NpBi [15,23] transform directly from (B1) to (B2) at 5 and 8 GPa, respectively, whereas AmBi [14] transforms directly from (B1) to tetragonal at 14 GPa. CmBi [15] on the other hand, exhibits an intermediate CsCl (B2) structure at 12 GPa before its final tetragonal phase, which appears at 20 GPa. In the case of the monoantimonides NpSb [24] transforms directly from the (B1) to tetragonal at 12 GPa and PuSb [24,25] also shows an intermediate (B2) phase at 18 GPa before becoming tetragonal at 42 GPa identical to CmBi. For PuSb, it is believed that Sb–Sb bonding leads to the tetragonal structure and that the CsCl phase appears only above a certain ratio of cation to anion radii. For the higher actinides, it is probable that the transitions occur due to f–p (An f and Bi p electrons) interactions. These differences are believed to be due in part to the different An–An and An–Bi distances encountered across the series, in addition to the presence of localised and itinerant f electrons. These factors will be discussed in a forthcoming publication dealing with AmBi [14].
4. Conclusions
Acknowledgements
This present work extends previous studies performed on the pressure behaviour of actinide monobismuthides to PuBi. This actinide monobismuthide was of particular interest to explore for unusual behaviour under pressure, as Pu is the last member of the actinide series where the 5f electrons are normally delocalised in the elemental state. We have concluded that the pressure behaviour of PuBi observed up to 50 GPa is in general similar to that of other actinide monobismuthides. The appearance of both an intermediate tetragonal
YM thanks the EUROPEAN Commission for support given in the frame of the program ‘Human Capital and Mobility’.
References [1] U. Benedict, S. Dabos-Seignon, S. Heathman, J.P. Dancausse, M. Gensini, E. Gering, J.C. Spirlet, High-Pressure Phases and Compressibility of Neptunium and Plutonium Compounds. In: L.R. Morss, J.
´ et al. / Journal of Alloys and Compounds 284 (1999) 65 – 69 Y. Meresse
[2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13]
Fuger (Eds.), Transuranium Elements A Half Century, American Chemical Society, Washington DC, Chapter. 38, 1992, p. 396. U. Benedict, J. Less-Common Metals 128 (1987) 7. ´ O. L. Gerward, J. Staun Olsen, U. Benedict, S. Dabos, J.-P. Itie, Vogt, High Temp. High Press. 20 (1988) 545. J. Staun Olsen, L. Gerward, U. Benedict, H. Luo, O. Vogt, High Temp. High Press. 20 (1988) 553. L. Gerward, J. Staun Olsen, U. Benedict, S. Dabos, O. Vogt, High Pressure Res. 1 (1989) 235. ´ O. J. Staun Olsen, L. Gerward, U. Benedict, S. Dabos, J.-P. Itie, Vogt, High Pressure Res. 1 (1989) 253. ` Physica S. Dabos, C. Dufour, U. Benedict, J.-C. Spirlet, M. Pages, B. 144 (1986) 79. ´ J. LessS. Dabos Seignon, U. Benedict, J.-C. Spirlet, M. Pages, Common Met. 153 (1989) 133. S. Dabos-Seignon, U. Benedict, S. Heathman, J.-C. Spirlet, M. ´ J. Less Common Met. 160 (1990) 35. Pages, M. Gensini, E. Gering, S. Heathman, U. Benedict, J.-C. Spirlet, High Pressure Res. 2 (1990) 347. U. Benedict, J. Alloys Comp. 193 (1993) 88. U. Benedict, J. Alloys Comp. 223 (1995) 216. M. Gensini, R.G. Haire, U. Benedict, F. Hulliger, J. Rebizant, High Pressure Phases and Compressibility of the B1-Type compounds CmBi, UBi and NpSe. Annual Report of the Institute for Transuranium Elements, 1991, EUR 13815 EN, p. 157.
69
[14] S. Heathman, R.G. Haire, U. Benedict, Energy dispersive X-ray diffraction analysis of AmBi under pressure. Annual Report of the Institute for Transuranium Elements, 1994, EUR 16152 EN, p. 144. [15] M. Gensini, R.G. Haire, U. Benedict, F. Hulliger, J. Rebizant, Physica B. 190 (1993) 75. [16] J.C. Spirlet, O. Vogt, Sample preparation and crystal growth for solid state actinide research. In: Handbook on the Physics and Chemistry of the Actinides, Vol. 1, Chapter 2, 1984, p. 79. [17] JCPDS card: 41-1188. [18] H.K. Mao, P.M. Bell, J.W. Shaner, D.J. Steinberg, J. Appl. Phys. 49 (1978) 3276. [19] E. Hovestreydt, E. Parthe, U. Benedict, ENDIX Report EUR 10874 (1987), J. Appl. Cryst. 21 (1988) 282. [20] E. Williams, Report IS-1052, Ames Laboratory at Iowa State, University of Science and Technology, Ames, IA, USA, 1964. [21] F. Birch, Phys. Rev. 71 (1947) 809. [22] F.D. Murnaghan, Am. J. Math. 49 (1937) 235. [23] U. Benedict, S. Dabos-Seignon, J.P. Dancausse, M. Gensini, E. Gering, S. Heathman, H. Luo, J. Staun Olsen, L. Gerward, R.G. Haire, J. Alloys Comp. 181 (1992) 1. [24] S. Dabos-Seignon, U. Benedict, S. Heathman, J.C. Spirlet, J. LessCommon Met. 160 (1990) 35. [25] U. Benedict, S. Dabos-Seignon, H. Luo, S. Heathman, J. Nucl. Mat. 166 (1989) 48.