Professor Yoed Tsur

The Technion was founded in 1912 in Haifa and is the oldest university in Israel. The university offers degrees in science and engineering, and related fields. Technion is noted as a global pioneer in multidisciplinary research into fields including energy, nanotechnology and life science. It has 18 academic departments and 52 research centers and over 13,000 students. Since its founding, it has awarded over 95,000 degrees and its graduates are cited to have brought the unique skills and penchant for innovation which helped conceive and consolidate the modern State of Israel. Technion graduates comprise the majority of Israeli-educated scientists and engineers, constituting over 70% of the country’s founders and managers of high-tech industries. 80% of Israeli NASDAQ companies are led by Technion graduates.

The research at Tsur's group in the Wolfson Department of Chemical Engineering spans from point defect chemistry of electroceramic materials, through nanomaterials synthesis to electrochemical measurements of solids and solid state devices. Within TEPS, the group is focusing on adapting a novel method for the analysis of impedance spectroscopy results for electrochemical devices, starting with super-capacitors. Impedance spectroscopy can be viewed as the extension of dc resistivity measurements into ac, i.e., the ratio V/I at different frequencies. This is a complex function of the frequency where the real and imaginary parts should ideally obey certain integral transforms. The Holy Grail then, is to find a sound physical interpretation to the experimental results.

Although the measurement method is known and applied for decades, the traditional way of analysis suffers from many drawbacks. What usually one does is to find an equivalent circuit that would generate a similar response to the ac stimulus, and then try to assign a physical meaning to the various elements of that circuit. The main problems with this approach are: (a) equivalent circuits are not unique: there are many different circuits that solve a particular problem equally well (it is an ill-posed problem); (b) the old method is prone to over fitting: when one assumes a certain circuit based on theory, it may have too many free parameters; (c) some of the common circuit elements are very loosely related to any physical meaning. The new approach solves the ill-posed problem by finding a functional form of the underlying distribution of relaxation times (DFRT) in the sample. There are other methods in the literature that also find a DFRT, but all of those deconvolution methods are finding it by Fourier (or another integral) transform. This means that a filter must be used and the result is a point-by-point one rather than an analytic function. Hence, the novel method developed here has also clear advantages over the known deconvolution methods.