The main goal of the project is the investigation of extrinsic sources that degrade the complex permittivity of low-loss dielectrics/ ferroelectrics in microwaves, millimeter-waves, and submillimeter-waves. The studies will be focused on the broad-band frequency behavior of bulk dielectrics and thin/thick film ferroelectrics with different microstructures. In this sense, samples will be prepared by using several experimental techniques (conventional ceramic technology, spark plasma sintering, radio frequency–magnetron sputtering, and pulsed laser ablation deposition). Apart of usual structural and morphological characterizations (X-ray diffraction, electron microscopy), the extrinsic contribution to the complex permittivity will be investigated with following innovative techniques: terahertz time-domain spectroscopy (THz-TDS), split post dielectric resonator, and spectroscopic ellipsometry. It is aimed to solve through the analysis of the synthesis - microstructure - properties cycle a very important scientific and applied problem of national and international interest. This knowledge will allow to achieve the intrinsic limit of dielectric properties of materials with low-loss microwaves, millimeter-waves, and submillimeter-waves.

Dr. Liviu Nedelcu - project leader

Dr. George Stan - postdoctoral researcher

Dr. Aurelian-Cătălin Gâlcă – postdoctoral researcher

Dr. Cristina Chirila - postdoctoral researcher

Mihai Burdusel - PhD student

• Low-loss zirconium tin titanate (ZST) ceramics by conventional ceramic technology
• Ultra low-loss barium magnesium tantalate (BMT)  ceramics by conventional ceramic technology
• High density (> 99.9%) zirconium tin titanate (ZST) ceramics with low-loss by spark plasma sintering
• High density (> 98.5%) barium magnesium tantalate (BMT) ceramics with low-loss by spark plasma sintering
• Single phase barium strontium titanate (BST) ferrolectric thick films by PLD
• Single phase barium strontium titanate (BST) ferrolectric thick films by RF magnetron sputtering
• A novel approach for the extraction of the dielectric properties of the thick film from the THz-TDS data

Papers presented at conferences

1. L. Nedelcu, G. Annino, C. Chirila, L. Trupina, A. C. Galca, M. G. Banciu, Terahertz and optical properties of Ba_0.6Sr_0.4TiO₃ thick films grown by PLD, EMRS 2019 Spring Meeting, 27 – 31 May 2019, Nice, France

2. L. Nedelcu, C. Chirila, G. E. Stan,  A. C. Galca, L. Hrib, L. Trupina,  C. D. Geambasu, M. G. Banciu, Terahertz characterization of (Ba,Sr)TiO₃ ferroelectric films grown by PLD and RF magnetron sputtering, 20th International Balkan Workshop on Applied Physics and Materials Science, 14-17 July 2019, Constanta, Romania

Published papers

1. L. Nedelcu, M. Burdusel, M. A. Grigoroscuta, C. D. Geambasu, M. G. Banciu, P. Badica, Extrinsic absorption in spark plasma sintered Zr_0.8Sn_0.2TiO₄ ceramics investigated by terahertz time-domain spectroscopy, IEEE Proceedings of the 44th International Conference on Infrared, Millimeter, and Terahertz Waves, 1-6 September 2019, Paris, France.

https://doi.org/10.1109/IRMMW-THz.2019.8873760

2. M.G. Banciu, D.C. Geambasu, L. Nedelcu, L. Trupina, Frequency selective surfaces with hexagonal elements for millimeter waves applications, Proceedings of the 42th International Semiconductor Conference, 9-11 October 2019, Sinaia, Romania

https://doi.org/10.1109/SMICND.2019.8923621

3. G. Banciu, L. Nedelcu, T. Furuya, L. Hrib, D. C. Geambasu, L. Trupina, D. Pantelica, M.-D. Mihai, M. Tani, Experimental study of terahertz response from some ferroelectric and dielectric materials, Proceedings of the Romanian Academy, Series A 20 (2019) 353. (IF=1.294)

4. L. Nedelcu, G. Annino, C. Chirila, L. Trupina, A. C. Galca, M. G. Banciu, Investigation of Ba_0.6Sr_0.4TiO₃ thick films by means of a novel THz-TDS approach, Applied Surface Science 506, (2020) 144807.  (IF=6.707)

https://doi.org/10.1016/j.apsusc.2019.144807

5. L. Nedelcu, C. D. Geambasu, M. Enculescu, M. G. Banciu, Intrinsic dielectric loss in Zr_0.8Sn_0.2TiO₄ ceramics investigated by terahertz time domain spectroscopy, Materials 14 (2021) 2016. (IF=3.623)

https://doi.org/10.3390/ma14010216

Dr. Liviu Nedelcu

Scientific researcher rank II

Laboratory of Complex Heterostructures and Multifunctional Materials

Phone: +40-(0)21-2418 123

nedelcu@infim.ro