Technique: Dielectric Permittivity ε*(ω) |
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The dielectric laboratory offers a variety of highly sensitive and mostly automated equipment for impedance measurements which directly yield the frequency-domain dielectric function ε*(ω). The orientational motion of molecules as well as the translational motion of ions can be studied as a function of temperature (25 K to 475 K), in a wide range of frequencies, 10 μHz to 10 MHz. |
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Typical components for a frequency domain measurement of the impedance or dielectric function
ε*(ω). For frequencies between
10 μHz and 10 MHz we use a gain-phase analyser Solartron SI-1260
and a transimpedance amplifier DM-1360, which converts low currents to measurable voltages over
the entire frequency range. [56] |
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We focus mainly on the dynamics in the viscous regime of glass-forming materials near the glass transition temperature [47, 51, 69, 77, 79, 85, 107, 111, 125, 132, 133, 140, 158, 168, 183]. In order to resolve even very small current signals properly, the transimpedance amplifiers 'DM-1360' and 'DM-1370' developed in our lab are employed [56]. |
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Example of impedance measurements using the SI-1260 analyzer combined with the DM-1360 and the
DM-1370 amplifiers. Impedances as high as 3×1015 Ω are being measured by analysing
amplitude and phase of a 10-15 A current at 10-5 Hz. Capacity changes of
10-15 F and loss tangents near tanδ = 2×10-5 can be resolved with our system.
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Schematic outline of the dual-capacitor and its connections to the SI-1260 gain/phase
analyzer as used in the simultaneous dielectric measurements: The generator
signal 'GEN' is fed to the common center electrode and via a resistor of R = 1 kΩ
to the current input 'I', the outer electrode currents are routed to separate transimpedance
amplifiers, 'I → V', and their outputs are analyzed by the V-1 and V-2 inputs of the analyzer.
The setup facilitates the detection of minute differences of two samples that are subject to the
same temperature, thermal history, and electric field.
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Other dielectric equipment in our lab: Andeen-Hagerling Ultraprecision Capacitance Bridge AH-2700A (50 Hz - 20 kHz, tanδ > 4×10-8) Solartron SI-1260 10 μHz - 30 MHz gain/phase analyzer Stanford-Research Lock-In SR-830 (1 mHz - 102 kHz) Hewlett-Packard Impedance Bridge HP-4284A (20 Hz - 1 MHz) Nicolet Sigma 100 4channel 100MS/s 14 bit digital scope Stanford-Research DS-345 1 μHz - 30 MHz synthesized function generator Mestec DM-1360 & DM-1370 transimpedance amplifiers Our dielectric cells: |
[85] |
[213] |
[183] |
[209] |
[202] |
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Reference numbers refer to the list of publications |
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Experimental techniques:
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Selected projects:
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