@article{MellingerFruebingPrescheretal.1999,
  author    = {Mellinger, Axel and Fr{\"u}bing, Peter and Prescher, Dietrich and Gerhard, Reimund},
  title     = {Dielectric spectra of a partially fluorinated chromophore / amorphous Teflon AF guest-host system},
  year      = {1999},
  language  = {en}
}
@article{MellingerWegenerWirgesetal.2001,
  author    = {Mellinger, Axel and Wegener, Michael and Wirges, Werner and Gerhard, Reimund},
  title     = {Thermally stable dynamic piezoelectricity in sandwich films of porous and non-porous amorphous fluoropolymer},
  year      = {2001},
  language  = {en}
}
@article{GonzalezMellingerGerhardetal.2002,
  author    = {Gonzalez, Francisco Camacho and Mellinger, Axel and Gerhard, Reimund and Santos, Lucas F. and Faria, Roberto M.},
  title     = {Photo-stimulated discharge of highly insulating polymers (PTFE and PETP)},
  isbn      = {0-7803-7502-5},
  year      = {2002},
  language  = {en}
}
@article{MellingerGonzalezGerhardetal.2002,
  author    = {Mellinger, Axel and Gonzalez, Francisco Camacho and Gerhard, Reimund and Santos, Lucas F. and Faria, Roberto M.},
  title     = {Phototstimulated discharge of corona and electron-beam charged electret polymers},
  isbn      = {0-7803-7560-2},
  year      = {2002},
  language  = {en}
}
@article{MellingerGonzalezGerhard2003,
  author    = {Mellinger, Axel and Gonzalez, Francisco Camacho and Gerhard, Reimund},
  title     = {Ultraviolet-induced discharge currents and reduction of piezoelectric coefficient in cellular polypropylene films},
  year      = {2003},
  language  = {en}
}
@article{Mellinger2004,
  author    = {Mellinger, Axel},
  title     = {Unbiased iterative reconstruction of polarization and space-charge profiles from thermal-wave experiments},
  issn      = {0957-0233},
  year      = {2004},
  abstract  = {The thermal-wave technique or laser-intensity modulation method is an important tool for the non-destructive probing of space-charge and polarization profiles in electrets. Analysing the experimental data requires solving a Fredholm integral equation which is known to be an ill-conditioned problem. This paper presents an iterative approach that is capable of reconstructing inherently unsmooth distributions. The deviations from the true profiles are slightly smaller than those obtained with Tikhonov regularization, while the computational burden is not a limiting factor on modem personal computers. The optimum number of iterations is estimated using the randomized generalized cross- validation technique. Results are shown for a number of model distributions, as well as for experimental data from a layered polyvinylidene fluoride film sandwich},
  language  = {en}
}
@article{MellingerCamachoGonzalezGerhard2004,
  author    = {Mellinger, Axel and Camacho Gonz{\´a}lez, Francisco and Gerhard, Reimund},
  title     = {Photostimulated discharge in electret polymers : an alternative approach for investigating deep traps},
  year      = {2004},
  abstract  = {The stability of space charge in electrets such as polytetrafluoroethylene (PTFE), polyethylene terephthalate (PETP) and polypropylene (PP) under ultraviolet irradiation has been investigated using photostimulated discharge spectroscopy. While only weak discharge currents were observed in PTFE coated with semitransparent gold electrodes, up to 15 pA/cm(2) were found in PETP around the UV absorption edge near 310 nm. Space charge profiles obtained with the piezoelectrically generated pressure step method indicate that near-surface charges were almost completely removed. In PP foam, recent findings of a UV-reduced d(33) coefficient were confirmed for exposure times of up to 3.5 h, and a discharge peak at 200 urn could be assigned to the charges stored on the surfaces of the voids. The unique morphology and the (quasi-) piezoelectric properties of cellular PP make it a role model for the future investigation of charge storage in electrets},
  language  = {en}
}
@phdthesis{Mellinger2004,
  author    = {Mellinger, Axel},
  title     = {Charge storage in electret polymers: mechanisms, characterization and applications},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-5689},
  school      = {Universit{\"a}t Potsdam},
  year      = {2004},
  abstract  = {Electrets are materials capable of storing oriented dipoles or an electric surplus charge for long periods of time. The term "electret" was coined by Oliver Heaviside in analogy to the well-known word "magnet". Initially regarded as a mere scientific curiosity, electrets became increasingly imporant for applications during the second half of the 20th century. The most famous example is the electret condenser microphone, developed in 1962 by Sessler and West. Today, these devices are produced in annual quantities of more than 1 billion, and have become indispensable in modern communications technology. Even though space-charge electrets are widely used in transducer applications, relatively little was known about the microscopic mechanisms of charge storage. It was generally accepted that the surplus charges are stored in some form of physical or chemical traps. However, trap depths of less than 2 eV, obtained via thermally stimulated discharge experiments, conflicted with the observed lifetimes (extrapolations of experimental data yielded more than 100000 years). Using a combination of photostimulated discharge spectroscopy and simultaneous depth-profiling of the space-charge density, the present work shows for the first time that at least part of the space charge in, e.g., polytetrafluoroethylene, polypropylene and polyethylene terephthalate is stored in traps with depths of up to 6 eV, indicating major local structural changes. Based on this information, more efficient charge-storing materials could be developed in the future. The new experimental results could only be obtained after several techniques for characterizing the electrical, electromechanical and electrical properties of electrets had been enhanced with in situ capability. For instance, real-time information on space-charge depth-profiles were obtained by subjecting a polymer film to short laser-induced heat pulses. The high data acquisition speed of this technique also allowed the three-dimensional mapping of polarization and space-charge distributions. A highly active field of research is the development of piezoelectric sensor films from electret polymer foams. These materials store charges on the inner surfaces of the voids after having been subjected to a corona discharge, and exhibit piezoelectric properties far superior to those of traditional ferroelectric polymers. By means of dielectric resonance spectroscopy, polypropylene foams (presently the most widely used ferroelectret) were studied with respect to their thermal and UV stability. Their limited thermal stability renders them unsuitable for applications above 50 °C. Using a solvent-based foaming technique, we found an alternative material based on amorphous Teflon® AF, which exhibits a stable piezoelectric coefficient of 600 pC/N at temperatures up to 120 °C.},
  subject      = {Elektret},
  language  = {en}
}
@article{LangMellinger2005,
  author    = {Lang, Sidney B. and Mellinger, Axel},
  title     = {A package of Mathematica programs for training students in the use of LIMM and its analysis},
  year      = {2005},
  abstract  = {A package of programs written using the symbolic mathematics program, Mathematicatrademark, has been developed. Its principal usage is in teaching the LIMM method to students and demonstrating data analysis by means of the Polynomial Regularization Method (PRM). A large number of variables can be changed in the program and their effects can be shown graphically. Students at the University of Potsdam and Monash University have used the program successfully},
  language  = {en}
}
@article{MellingerSinghGerhard2005,
  author    = {Mellinger, Axel and Singh, Rajeev and Gerhard, Reimund},
  title     = {Fast thermal-pulse measurements of space-charge distributions in electret polymers},
  issn      = {0034-6748},
  year      = {2005},
  abstract  = {Space-charge depth profiles in various electret polymers have been measured in both the time and the frequency domain using thermal pulses and waves, respectively. A comparison of the two techniques on corona-charged polytetrafluoroethylene showed that the thermal-pulse method yielded similar results as the thermal-wave technique, but approximately 20-50 times faster. The article discusses sensitivity limitations as well as possible applications, including the real-time monitoring of space-charge decay under UV irradiation. (C) 2005 American Institute of Physics},
  language  = {en}
}