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  • 1
    Electronic Resource
    Electronic Resource
    Lead-free ruthenium-based thick-film resistors: a study of model systems (1991)
    Springer
    Journal of materials science 2 (1991), S. 46-53 
    Details
    ISSN: 1573-482X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A model system of thick-film resistor (TFR) was prepared starting from RuO2 powders and a lead-free glass. The microstructural development was investigated by scanning and transmission electron microscopies, energy dispersive X-ray fluorescence, X-ray diffraction, thermogravimetry and other complementary techniques. The electrical properties of the resistors were analysed with particular attention to sheet resistance, temperature coefficient of resistance, size effects and piezoresistive properties. It was found that these simple systems are interesting with respect to their stability in ageing tests at relatively high temperatures but they are not promising for high-temperature piezoresistive gauges because of low strain sensitivity. Some samples were also prepared with a Bi2Ru2O7; a notable exchange reaction occurs between the conductive grains and the glass matrix which prevents the formation of pyrochlore-type based resistors with this glassy matrix.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00695004
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  • 2
    Electronic Resource
    Electronic Resource
    Magnetic properties of ferrihydrite (1986)
    Springer
    Hyperfine interactions 27 (1986), S. 329-332 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The magnetic properties of a sample of synthetic ferrihydrite have been investigated by use of Mössbauer spectroscopy. The area ratios of the Mössbauer lines are not significantly changed by application of magnetic fields at 5 K, indicating an amorphous magnetic structure. An average magnetic moment per particle of 3.1×10−21 JT−1 was estimated from the dependence of the hyperfine splitting of the Mössbauer spectra on external magnetic fields at 80 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02354773
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  • 3
    Electronic Resource
    Electronic Resource
    Magnetoresistance of RuO2-Based Thick Film Resistors (1998)
    Springer
    Journal of low temperature physics 112 (1998), S. 355-371 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In a series of samples whose composition was systematically changed, we have studied the magnetoresistance (ΔR/R = [R(B)-R]/R) of RuO 2 -based thick film resistors (TFR's) in magnetic fields (B) up to 20 Tesla and in a temperature range (1.2 K 〈 T 〈 40 K) in which their resistance exhibits insulating behavior at the boundary between the strong and the weak localization. At the higher temperatures, ΔR/R exhibits a positive bump that does not depend on the RuO 2 concentration but it changes with the concentration of magnetic Mn impurities diluted in the glassy matrix. For T ≤ 20 K magnetoresistance is entirely negative and it has a quadratic magnetic field dependence at low field. We use the weak localization theory to relate these features of the high temperature magnetoresistance to the composition of TFR's. At low temperature (T 〈 4.2 K) the negative magnetoresistance shows some peculiarities. The quadratic term shrinks within a vanishing magnetic field range and the magnetoresistance linearly increases in a wide range of B. At the strongest fields and the lowest temperature ΔR/R shows a tendency to saturation. Although these results do not enable to discriminate among different mechanisms, we note that the low temperature (T 〈 4.2 K) behavior is essentially consistent with recent theory of Nguen et al.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022336702261
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  • 4
    Electronic Resource
    Electronic Resource
    Low Temperature Electronic Transport in RuO2-Based Cermet Resistors (1997)
    Springer
    Journal of low temperature physics 109 (1997), S. 461-475 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have studied the temperature (T) dependence of resistance (R) of RuO2-based thick films down to 1.2 K. Samples were prepared from inks containing conductive RuO2 powders (⩽ 10% wt.), high lead-silicate glass particles and Mn (⩽ 1.4% wt.). We found that the resistance fits the exponential law R = R 0 exp(T 0/T)x with x = 1/4 and the most resistive samples show a cross-over to the x = 1/2 regime as the temperature decreases. Both the fitting parameters R 0 and T 0 scale down as the RuO2 fraction increases and they are affected in a similar way by a change of the Mn content. The presence of the two regimes is similar to that observed in n-type GaAs [Phys. Rev. B 39, 8059 (1989)] and n-type CdSe [Phys. Rev. Lett. 64, 2687 (1990)] whilst it disagrees with the behaviour predicted for grain to grain hopping [Phys. Rev. B 27, 2583 (1983)] and with that expected for resonant tunneling between metallic particles [J. Appl. Phys. 48, 5152 (1977)]. We conclude that in our systems the driving charge transport mechanism is electron hopping within the glassy matrix. Since in our case the hopping length is of the same order of the localization length, the puzzling questions arising from our experiments are whether and how the variable range hopping model can be extended beyond its conventional limits.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s10909-005-0096-y
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  • 5
    Electronic Resource
    Electronic Resource
    Low temperature electronic transport in RuO2-based cermet resistors (1997)
    Springer
    Journal of low temperature physics 109 (1997), S. 461-475 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have studied the temperature (T) dependence of resistance (R) of RuO2-based thick films down to 1.2 K. Samples were prepared from inks containing conductive RuO2 powders (〈-10% wt.), high lead-silicate glass particles and Mn (≤1.4% wt.). We found that the resistance fits the exponential lawR=R 0 exp (T 0/T)x with x=1/4 and the most resistive samples show a cross-over to the x=1/2 regime as the temperature decreases. Both the fitting parametersR 0 andT 0 scale down as the RuO2 fraction increases and they are affected in a similar way by a change of the Mn content. The presence of the two regimes is similar to that observed inn-type GaAs [Phys. Rev. B39, 8059 (1989)] andn-type CdSe [Phys. Rev. Lett.64, 2687 (1990)] whilst it disagrees with the behaviour predicted for grain to grain hopping [Phys. Rev. B27, 2583 (1983)] and with that expected for resonant tunneling between metallic particles [J. Appl. Phys.48, 5152 (1977)]. We conclude that in our systems the driving charge transport mechanism is electron hopping within the glassy matrix. Since in our case the hopping length is of the same order of the localization length, the puzzling questions arising from our experiments are whether and how the variable range hopping model can be extended beyond its conventional limits.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02396906
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  • 6
    Electronic Resource
    Electronic Resource
    Magnetoresistive properties of Ni-based thick films (1990)
    Springer
    Journal of materials science 1 (1990), S. 118-122 
    Details
    ISSN: 1573-482X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Investigations have been carried out on the electrical properties of nickel-based films prepared from air-fireable pastes on alumina substrates. In particular, magnetoresistive effects have been studied as a function of temperature, strength and direction of the magnetic field. These properties were determined in films at different stages of formation, i.e. prepared at various peak firing temperatures and dwell times, and compared with those displayed by nickel foils. These results provide the basis for the development of magnetoresistive thick-film sensors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00694920
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  • 7
    Electronic Resource
    Electronic Resource
    On anomalously magnetic basalt lavas from Stardalur Iceland (1990)
    Springer
    Hyperfine interactions 57 (1990), S. 2209-2214 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In an attempt to explain an exceptionally strong magnetic anomaly near Stardalur, SW-Iceland, a 200 m deep hole was drilled into its centre and the core subjected to various mineralogical and geophysical measurements. In Mössbauer spectra of bulk samples from depths between 45 and 170 m the magnetic phase is predominant and consists of very pure magnetite. The area ratio for the components with hyperfine fields of 46 and 49 T is approximately 2. Comparison with spectra of selected basalt lavas showing similar magnetic properties indicates a distinctive difference. The strong remanent magnetism of the Stardalur samples can be explained by a combination of unusually high concentration in the rocks of pure magnetite, it's small grain size and a strong magnetic field appending its formation. It is suggested that both the composition of the magnetic phase and the strong magnetic field were brought about by hydrothermal alteration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02405787
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  • 8
    Electronic Resource
    Electronic Resource
    Decoupling of magnetically interacting crystallites of goethite (1986)
    Springer
    Hyperfine interactions 28 (1986), S. 549-552 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The magnetic properties of synthetic goethite, precipitated from a SiO2-containing Fe(III) solution, have been studied. The Mössbauer spectra show the coexistence of a quadrupole doublet and a magnetically split component in a large temperature range. The area ratio of these two components depends strongly on temperature, indicating a normal superparamagnetic behaviour of isolated crystallites. This is in contrast to the behaviour normally exhibited by pure samples of microcrystalline goethite, in which strong magnetic interactions among the crystallites lead to a superferromagnetic behaviour. The results show that the magnetic interactions among the crystallites are drastically diminished when amorphous SiO2 separates the goethite crystallites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02061508
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  • 9
    Electronic Resource
    Electronic Resource
    A study of the sump beaver's dental enamel (1986)
    Springer
    Hyperfine interactions 29 (1986), S. 1431-1434 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The nature of the iron-containing phase in the dental enamel of sump beaver incisors has been studied by use of Mössbauer spectroscopy. All iron atoms are found to be trivalent and to be present in particles exhibiting superparamagnetic relaxation. The iron-containing phase has Mössbauer parameters similar to those of ferritin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02399503
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