Seminar: Positron Spectroscopy Investigation of Structural Void Defects in Technological Materials

  • Date: 08 October 2025

Investigation of Structural Cavity Defects in Technological Materials by Positron Spectroscopy

Uğur YAHŞİ

Marmara University, Faculty of Science, Department of Physics, 34722 Göztepe, Istanbul

Place: Materials and Metallurgical Engineering, Recep Tayyip Erdoğan Complex 
Date: 15.10.2025 Time: 14:00

Abstract: Positron Annihilation Lifetime Spectroscopy (PALS) and Doppler Broadening Spectroscopy (DBS) are the two main measurement techniques in positron spectroscopy. These methods allow the study of angstrom-scale structural defects in materials. Nano-void defects are void spaces observed at the atomic or molecular scale (0.1-1 nm in diameter) in crystalline or amorphous structures. Positron techniques are a powerful tool to identify defect configurations that are directly related to the macroscopic properties of the material [1]. In this context, the technologically important studies carried out at the Marmara Positronium Laboratory (MARPOS) will be briefly introduced [2].

The PALS technique is a time spectroscopy technique based on the measurement of the time difference between the 1274 keV pre-gamma and the 511 keV extinction gamma. The DBS technique provides information about the momentum distribution of electrons in the medium by analyzing the Doppler broadening of the annihilation emission [1].

Some of the applications realized within MARPOS are as follows:

Ionic conductivity in PVdF-co-HFP/LiClO₄ polymer electrolytes [3],
The role of defects in the structural properties of doped ZnO nanoparticles,
Structural analysis of doped hydroxyapatite [4]
...
These studies are important in terms of revealing nanostructural defects by utilizing positrons and correlating them with the performance properties of materials.

Keywords: Positron Spectroscopy, PALS, DBS, Structural Defects, Nanomaterials

References:

[1] Y. C. Jean, et al., Principles and Applications of Positron & Positronium Chemistry, World Scientific Pub. Co., New Jersey, USA; Z. Yu, U. Yahsi, et.al., J. Polym. Sci. B: Polym. Phy., 32, 2637 (1994).

[2] Marmara University, Faculty of Science, Department of Physics, Positron/Positronium Research and Service Laboratory, http://positron-fzk-fen.marmara.edu.tr/

[3] Ionic Conductivity of PVdF-co-HFP with LiClO₄: Free Volume Effects Probing by PALS," U. Yahsi, H. Deligöz, et al., Radiation Effects and Defects in Solids, 174(3), 214-228 (2019).

[4] “Effects of sintering and zirconmullite doping on nanostructural vacancies of bovine hydroxyapatite by positron technique,” L.N. Akay, C. Kalkandelen, N. Akti, M. S. Sengul, C. Tav, U. Yahsi, Z. E. Erkmen, Journal of the American Ceramic Society, 106(5), 3220-3227 (2023).  (https://doi.org/10.1111/jace.18985)

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Notices

ADEP project has been accepted: "Obtaining high-density materials from nanomaterials synthesized by different methods by flash sintering technique and ..."

BAP project has been accepted: "Investigation of the Conductivity-Free Volume Mechanism of Li Solid Polymer Electrolytes Using Positron Techniques"

Our PhD student Dr. Zainab Raad successfully defended and completed her PhD thesis titled "Point defect investigation in Cu and Cr codoped ZnO with varying Cr content prepared via Sol-Gel method".

Our paper is published in Physica Scripta online by the title: "The impact of reactor neutrons on 6H-SiC followed by irradiation of 91.3 MeV Xe ions - Defects studies using positron annihilation spectroscopy"

A seminar on the introduction of the MARPOS laboratory and positron studies at the Institute of Clean Energy Technologies at Yıldız Technical University.

A seminar on the presentation of the MARPOS laboratory and positron studies at Istanbul University - Cerrahpaşa Institute of Nanotechnology and Biotechnology.

"Preparation and characterization of an acrylated-coumarin-containing photo-crosslinked thiol-ene network: Investigation of ..." has been published in Polymer Engineering and Science.

PhD student NourelHouda Ketita from Univ. of Skikda is visiting our lab. for her thesis study of Cu based films during 2-28.12.2024.

The paper with the title "Cation Vacancy-Mediated Ultrafast Hole Transport in CuBi2O4 Photocathodes” published in ChemSusChem

Muhamed Walid Khalimi, a PhD student at the University of Blida, is visiting our laboratory during October for his studies.

Prof. Mahdi Ghasemifard from Esfarayen University of Technology-Iran visits us for a year to work on the defects of nano-electroceramics materials.

Accepted paper in Materials Research Bulletin titled “A Novel Approach for the Atomic Scale Characterization of Li-ion Battery Components probed by Positron Annihilation Lifetime Spectroscopy,"

Accepted paper in J. Mol. Structure: "The Influence of Defects on the Structural, Optical, and Antibacterial Properties of Cr/Cu Co-Doped ZnO Nanoparticles"

Accepted paper: “Structural and dielectrical properties of PMMA/TeO2 composites in terms of free volume defects probed by positron annihilation lifetime spectroscopy”,

Emir Ardalı from Koç University has completed his MSc thesis in which some work has been contributed from MARPOS Lab.

The paper with the title “Proton pathways via free volumes: A positron annihilation lifetime spectroscopy (PALS) investigation of proton conductivity in SPEEK-PEG-TMOS composites” has been published at Colloids and Surfaces A: Physicochemical and Eng

Seminar at Dep. of Physics Engineering in İstanbul Technical University: Marmara Üniversitesi Pozitronyum Laboratuvarında Positron Spektroskopi Teknikleri: Teknolojik Malzemelerin Yapısal Boşluklarının İncelenmesi

Prof. Mostefa Ghamnia has been visiting the MARPOS lab from February 28th to March 6th, 2024.

The paper with the title “Proton pathways via free volumes: A positron annihilation lifetime spectroscopy (PALS) investigation of proton conductivity in SPEEK-PEG-TMOS composites” has been published at Colloids and Surfaces A: Physicochemical and Eng

“Dielectric relaxation time of PVAc in terms of hole fraction calculated from the theory of Simha-Somcynsky” has been published at Polymer.

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