High resolution alpha analyzer

BDS was used to investigate the molecular mobility of the materials in the frequency range from 10⁻¹ to 10⁶ Hz [15 ,57 ]. A periodic electric field with a small field strength was applied as an input and the time-dependent polarization was measured as output. The polarization arises from the orientation of permanent dipoles in the material and can be quantified using the complex dielectric function ε*(ω) = ε’(ω) – 𝑖ε″(ω) where ε′(ω) is the real (storage) part of the complex dielectric function and ε″(ω) is the imaginary (loss) part. The dielectric properties of the samples were measured in the temperature range from 173 to 503 K. BDS was carried out by a Novocontrol high-resolution ALPHA analyzer (Novocontrol Technologies, Montabaur, Germany) connected to an active sample cell. A Quatro Novocontrol cryosystem employing a temperature stability better than 0.1 K was used for temperature control. All samples were placed between two gold plated electrodes (Ø = 20 mm) in a parallel plate geometry. Gold electrodes were evaporated onto the surfaces of the samples in an ultrahigh vacuum (10⁻⁵ mbar) to establish a good electrical contact. The impedance Z*(ω) was measured and the complex dielectric function was calculated from the impedance.

The molecular
mobility as a molecular probe for structure was studied by broadband
dielectric spectroscopy (BDS). A high-resolution ALPHA analyzer connected
to a sample holder with an active sample head (Novocontrol, Montabaur,
Germany) was used to measure the complex dielectric permittivity ε*(f) = ε^′(f) – iε^″(f) in the frequency
range from 10^–1 Hz to 10⁶ Hz (f = frequency, ε^′ = real part, ε^″ = loss or imaginary part, ) in parallel plate geometry.^{60 (link)} To ensure a good electrical contact between
the sample and the electrodes of the sample holder (gold-coated brass
electrodes, 10 mm in diameter), gold electrodes with a diameter of
10 mm were evaporated on both sides of the film. The measurements
were carried out by isothermal frequency scans applying a temperature
program with several heating and cooling cycles in the range of 173
to 523 K. A Quatro cryosystem (Novocontrol) was used to control the
sample temperature, providing a temperature stability better than
0.1 K. During the whole measurement, the sample was kept in a dry
nitrogen atmosphere.