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Über die präparation und das supraleitende verhalten von CeRu2 und seiner Gd-, Mn-, Fe-, Co- und Ni-haltigen mischphasen
Solid State Communications,
Vol. 7,
pp. i—vu,
1969.
Pergamon Press.
Printed in Great Britain
Abstracts of Articles to be Published in The Journal of Physics and Chemistry of Solids ~JPhys. Chem. Solids (to be published)’ should be cited in references to material quoted from this section prior to the publication of the relevant article.
1.
ELECTROMIGRATION AND ASSOCIATED VOID FORMATION IN SILVER H.R. Patil and H.B. Huntington, Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14850
Electromigration in both 99.999% pure silver with about 1 ppm oxygen and 99.99% pure silver with about 40 ppm oxygen (presumably in the form of impurity oxides) has been measured using the vacancy flux method. The method consists of determining local volume changes in specimens subjected to a large d.c. current density (~-‘-~ 104A/cm 2) and a parabolic temperature distribution, which results from watercooling the specimen ends. As a result of improved temperature determination, the effective charge for electromigratiori was found to be about — 6.5e in contrast to the earlier reported value of about — 25e. Microscopic void formation on the cathode side and consequent sample elongation were observed only in the less pure silver and could not be induced in the purer material even when charged individually with oxygen or hydrogen. Some evidence indicated oxygen electromigration to the anode in silver and also an enhancement of the seif-electromigration of the latter in the presence of dissolved hydrogen.
Received 26 June 1969 2.
MIGRATION SOUS L’EFFET D’UN CHAMP ELECTRIQUE DE 110Ag ET DE ‘24Sb DANS L’ARGENT
N. Van Doan et G. Brebec, Commissariat l’Energie Atomique, Centre d’Etudes Nucléaires de Saclay, France
a
The most recent theories relative to the influence of anin electric fieldbriefly on therecalled. migrationIn of point defects metals are order to relate the various physical constants of the phenomenon, the flux of a solute is expressed in terms of ‘effective valences’ defined in
Thermodynamics of Irreversibles Processes. Experimental results show that atoms migrate towards the anode with effective valences 124Sb of —16 and —95 respectively for “°Agand at temperatures in the region of 900°C. Estimates were made on the resistivities that should be used in the different theories in order to compare their predictions with experimental results.
Received 24 February 1969 Revised 24 June 1969
3.
UBER DIE PRAPARATION UND DAS SUPRALEITENDE VERHALTEN VON CeRu 2 UND SEINER Gd—, Mn—, Fe—, Co— UND Ni—HALTIGEN MISCHPHASEN M. Wilhelm u. B. Hillenbrand, Aus dem Forschungslaboratorium Erlangen der Siemens AG
Durch geeigriete Glühbehandlung wurden einphasige Proben von CeRu 2 und homogene
ii
ABSTRACTS OF PAPERS TO APPEAR IN
Mischkristalle des Typs Ce
1~Gd~Ru2uiid CeRu2~Me~(Me = Mn, Fe, Co, Ni) bergestellt. Reines CeRu2 hat einen Sprungpunkt von 6,2°K. Die T~-Absenkung bei Zusatz von Gd ist proportional zur 4. Potenz der GdRu2-Konzentration. Bis etwa 13 Mol% GdRu2 sind die Mischkristalle supraleitend (T~ 3,8°K),bei höheren Konzentrationen werden die Proben ferromagnetisch. Bei Zugabe von CeMe2 erfolgt eine= praktisch lineare T~-Absenkung, Me Fe und Mn etwa 10 mal gröBer istdie alsfür bei Me = Co und Ni. Geringe Mengen Fe in dem für die Präparation verwendeten Cer wurden durch Zonenschmelzen entfernt.
J.
PHYS. CHEM. SOLIDS
Vol.7, No.21
in each sequence when plotted against nearest neighbor distance. In the same way, ultrasonic data on the pressure derivatives of the elastic constants have been reviewed and, in the case of NaBr, Na!, KF and K!, measured. The resulting smooth thermodynamic data have been used to obtain values of the constant volume temperature coefficient of the isothermal bulk modulus, dlnBT/dT)V and of dBT/dP)T. The former4deg~ is found to halide be roughly constantIt at —0.7 inx the 10 for both sequences. arises vibrational entropy of the crystal and appears as a correction in expressions giving the repulsive exponent in the two-parameter empirical Born model. The usual procedure of using compression
Single phase samples of CeRu 2 and homogeneous mixed crystals of the formula Ce1 -x Gd~Ru2 and CeRu 2_~Me~ (Me = Mn, Fe, Co, Ni) have been prepared by means of an appropriate annealing process. Pure CeRu2 becomes superconducting at T~= 6.2°K. In mixed crystals Ce1_~Gd~Ru2,T~decreases proportional to the fourth power of the GdRu 2 concentration. Superconductivity extends up to the amount of about 13 mole-% GdRu 2 (T~ 3,8°K); alloys exceeding this concentration are ferromagnetic. When adding CeMe2 a linear depression of T~has been observed. The gradient of this depression is about one order of magnitude greater with Me = Fe or Mn than with Me = Co or Ni. Small amounts of iron which were present in the available cerium metal have been removed by zone melting.
data to obtain dlnBT/dT) ~results in an erratic correction that occasionally amounts to more than 10 per cent of the repulsive parameter; on the other hand, the ultrasonically based correction is strikingly smooth at about 2 per cent. Experimental values of dBT/dP) Tare nearly invariant among these eight alkali halides at a value of 5.4. The Born model correctly predicts this magnitude but also predicts a systematic trend with repulsive exponent significantly greater than that found. Born—Hildebrand equations of state based on the ultrasonic parameters should provide improved estimates of V(P) relations; these do compare fairly well with X-ray data for NaF, NaCl and Na! to pressures on the order of the bulk modulus. Neither comparison with experiment will distinguish, however, for the whole group between the version of the Born model based on a power law repulsive potential and that based on an exponential law.
Received 16 May 1969 Received 1 August 1969 4.
ULTRASONIC PARAMETERS IN THE BORN MODEL OF THE SODIUM AND POTASSIUM HALIDES R.W. Roberts, Case Western Reserve University, Cleveland, Ohio and Charles S. Smith, University of North Carolina, Chapel Hill, North Carolina
Available experimental data at 295°K on the ultrasonic elastic constants and their temperature variation, the specific heat, and the thermal expansion of the sodium and potassium halides have been collected and inspected for smoothness
5.
QUANTUM THEORY OF FERROELECTRICITY — I. SPECTRAL ANALYSIS L. Novakovié, Department of Physics, University of Toronto, Toronto 5, Ontario, Canada
Using the method of second quantization the proton dynamics in hydrogen-bonded ferroelectrics is formulated. The general expression for the potential energy of the system of protons due to the presence of heavy ions is related to the
Vol. 7,
pp. i—vu,
1969.
Pergamon Press.
Printed in Great Britain
Abstracts of Articles to be Published in The Journal of Physics and Chemistry of Solids ~JPhys. Chem. Solids (to be published)’ should be cited in references to material quoted from this section prior to the publication of the relevant article.
1.
ELECTROMIGRATION AND ASSOCIATED VOID FORMATION IN SILVER H.R. Patil and H.B. Huntington, Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14850
Electromigration in both 99.999% pure silver with about 1 ppm oxygen and 99.99% pure silver with about 40 ppm oxygen (presumably in the form of impurity oxides) has been measured using the vacancy flux method. The method consists of determining local volume changes in specimens subjected to a large d.c. current density (~-‘-~ 104A/cm 2) and a parabolic temperature distribution, which results from watercooling the specimen ends. As a result of improved temperature determination, the effective charge for electromigratiori was found to be about — 6.5e in contrast to the earlier reported value of about — 25e. Microscopic void formation on the cathode side and consequent sample elongation were observed only in the less pure silver and could not be induced in the purer material even when charged individually with oxygen or hydrogen. Some evidence indicated oxygen electromigration to the anode in silver and also an enhancement of the seif-electromigration of the latter in the presence of dissolved hydrogen.
Received 26 June 1969 2.
MIGRATION SOUS L’EFFET D’UN CHAMP ELECTRIQUE DE 110Ag ET DE ‘24Sb DANS L’ARGENT
N. Van Doan et G. Brebec, Commissariat l’Energie Atomique, Centre d’Etudes Nucléaires de Saclay, France
a
The most recent theories relative to the influence of anin electric fieldbriefly on therecalled. migrationIn of point defects metals are order to relate the various physical constants of the phenomenon, the flux of a solute is expressed in terms of ‘effective valences’ defined in
Thermodynamics of Irreversibles Processes. Experimental results show that atoms migrate towards the anode with effective valences 124Sb of —16 and —95 respectively for “°Agand at temperatures in the region of 900°C. Estimates were made on the resistivities that should be used in the different theories in order to compare their predictions with experimental results.
Received 24 February 1969 Revised 24 June 1969
3.
UBER DIE PRAPARATION UND DAS SUPRALEITENDE VERHALTEN VON CeRu 2 UND SEINER Gd—, Mn—, Fe—, Co— UND Ni—HALTIGEN MISCHPHASEN M. Wilhelm u. B. Hillenbrand, Aus dem Forschungslaboratorium Erlangen der Siemens AG
Durch geeigriete Glühbehandlung wurden einphasige Proben von CeRu 2 und homogene
ii
ABSTRACTS OF PAPERS TO APPEAR IN
Mischkristalle des Typs Ce
1~Gd~Ru2uiid CeRu2~Me~(Me = Mn, Fe, Co, Ni) bergestellt. Reines CeRu2 hat einen Sprungpunkt von 6,2°K. Die T~-Absenkung bei Zusatz von Gd ist proportional zur 4. Potenz der GdRu2-Konzentration. Bis etwa 13 Mol% GdRu2 sind die Mischkristalle supraleitend (T~ 3,8°K),bei höheren Konzentrationen werden die Proben ferromagnetisch. Bei Zugabe von CeMe2 erfolgt eine= praktisch lineare T~-Absenkung, Me Fe und Mn etwa 10 mal gröBer istdie alsfür bei Me = Co und Ni. Geringe Mengen Fe in dem für die Präparation verwendeten Cer wurden durch Zonenschmelzen entfernt.
J.
PHYS. CHEM. SOLIDS
Vol.7, No.21
in each sequence when plotted against nearest neighbor distance. In the same way, ultrasonic data on the pressure derivatives of the elastic constants have been reviewed and, in the case of NaBr, Na!, KF and K!, measured. The resulting smooth thermodynamic data have been used to obtain values of the constant volume temperature coefficient of the isothermal bulk modulus, dlnBT/dT)V and of dBT/dP)T. The former4deg~ is found to halide be roughly constantIt at —0.7 inx the 10 for both sequences. arises vibrational entropy of the crystal and appears as a correction in expressions giving the repulsive exponent in the two-parameter empirical Born model. The usual procedure of using compression
Single phase samples of CeRu 2 and homogeneous mixed crystals of the formula Ce1 -x Gd~Ru2 and CeRu 2_~Me~ (Me = Mn, Fe, Co, Ni) have been prepared by means of an appropriate annealing process. Pure CeRu2 becomes superconducting at T~= 6.2°K. In mixed crystals Ce1_~Gd~Ru2,T~decreases proportional to the fourth power of the GdRu 2 concentration. Superconductivity extends up to the amount of about 13 mole-% GdRu 2 (T~ 3,8°K); alloys exceeding this concentration are ferromagnetic. When adding CeMe2 a linear depression of T~has been observed. The gradient of this depression is about one order of magnitude greater with Me = Fe or Mn than with Me = Co or Ni. Small amounts of iron which were present in the available cerium metal have been removed by zone melting.
data to obtain dlnBT/dT) ~results in an erratic correction that occasionally amounts to more than 10 per cent of the repulsive parameter; on the other hand, the ultrasonically based correction is strikingly smooth at about 2 per cent. Experimental values of dBT/dP) Tare nearly invariant among these eight alkali halides at a value of 5.4. The Born model correctly predicts this magnitude but also predicts a systematic trend with repulsive exponent significantly greater than that found. Born—Hildebrand equations of state based on the ultrasonic parameters should provide improved estimates of V(P) relations; these do compare fairly well with X-ray data for NaF, NaCl and Na! to pressures on the order of the bulk modulus. Neither comparison with experiment will distinguish, however, for the whole group between the version of the Born model based on a power law repulsive potential and that based on an exponential law.
Received 16 May 1969 Received 1 August 1969 4.
ULTRASONIC PARAMETERS IN THE BORN MODEL OF THE SODIUM AND POTASSIUM HALIDES R.W. Roberts, Case Western Reserve University, Cleveland, Ohio and Charles S. Smith, University of North Carolina, Chapel Hill, North Carolina
Available experimental data at 295°K on the ultrasonic elastic constants and their temperature variation, the specific heat, and the thermal expansion of the sodium and potassium halides have been collected and inspected for smoothness
5.
QUANTUM THEORY OF FERROELECTRICITY — I. SPECTRAL ANALYSIS L. Novakovié, Department of Physics, University of Toronto, Toronto 5, Ontario, Canada
Using the method of second quantization the proton dynamics in hydrogen-bonded ferroelectrics is formulated. The general expression for the potential energy of the system of protons due to the presence of heavy ions is related to the