In his research, Kouros Khamoushi investigated the microstructure of microwave dielectric rare-earth ceramic materials used as a high-quality filter material in the integrated circuits (IC) of smart mobile phones. These materials are essential for the functionality of oscillators, which act as electrical filters and are limited by the quality factor of the resonator. This means that only microwaves can pass through the material, while other waves are filtered out. The microstructures of ceramics significantly impact their dielectric properties.
Khamoushi used several techniques to characterize the rare-earth ceramic microstructure.
“Based on the obtained data, we can tune the electrical properties of the sample using doping to achieve a higher quality-factor. This, in turn, reduces the size, weight, and cost of materials,” he says.
This isthe first-time, a computational mathematical fractal analysis method has been used for rare-earth ceramics.
“The method I have developed allows us to scan the grain boundaries of ceramics and visualize their microstructure, demonstrating the novelty and importance of my work,” he adds.
Practically, fractal analysis and fractal regression methods are used to study the microstructure, surface topography, and dimensions of materials by means through a set of definite numbers. The systematic method developed by Khamoushi allows to improve the properties of the sample using a mix oxide routine. Powder material can be combined with other substances to obtain the desired quality.
The aim is to achieve material with a temperature resonant frequency () of zero and a high dielectric constant. CaTio3 has a very high dielectric constant of 145 but a very positive 439 ppm/°C. In contrast, lanthanum zinc titanium oxide (LZT) has a low temperature coefficient of -345 ppm/°C. CaTio3 cannot be used as a dielectric material on its own; however, by mixing it with LZT, it is possible to adjust its electronic properties.
“My approach can lead to the discovery of new promising ceramics for use in smart mobile phone communications. The insights from my research enable the prediction of the electronic properties of material before their installation in devices,” Khamoushi explains.
Khamoushi characterized microstructures and dielectric of the compound by a fractal analysis method to unambiguously define and improve the material’s microstructure. He tested a portion of grain boundaries of rare-earth ceramics to define their electronic properties using fractal analysis, highlighting the important and innovation of this research.
“Fractal analysis of the dataset computation precisely matches the contours to the microstructure, allowing further estimation of crystal structures that cannot be verified by the human eye. This is a valuable, inexpensive, and modern mathematical technique for analysing the microstructure of a sample,” he concludes.
The fractal analysis of lanthanum zinc titanium oxide and neodymium zinc titanium oxide in Khamoushi’s work produced accurate approximations and fruitful results.
Public defence on Friday 4 October
The doctoral dissertation of LicSc (Tech) in the field of electronic materials titled Fractal Analysis of Microwave Rare Earth Ceramics Materials for Telecommunications will be publicly examined at the Faculty of Engineering and Natural Sciences at Tampere University at 12.15 on Friday 4 October at Hervanta campus, Festia building, Pieni Sali 1 (FA032) (Korkeakoulunkatu 8, Tampere).
The opponent will be Professor Oldrich Zmeskal Brno University of Technology. The Custos will be Associate Professor Paola Vivo Faculty of Engineering and Natural Sciences.