The project is focused on the synthesis and characterization of some temperature-stable dielectric materials, which exhibit high relative permittivity and low-loss in the microwave domain. The correlation between dielectric parameters and composition, microstructure, crystal structure, etc. was followed up. In order to achieve the objectives, the dielectric materials were examined by means of various techniques such as X-ray diffraction, electron microscopy, microwave spectroscopy, and terahertz time-domain spectroscopy.

Project Objectives:

O.1 Investigations of some commercial materials and laboratory made dielectrics by using terahertz time-domain spectroscopy.
O.2 Correlation of the material preparation-characterization tasks with the dielectric properties.
O.3 Tailoring of the dielectric properties of materials by processing conditions.

Dr. Liviu NEDELCU, principal investigator

Dr. Marian Gabriel BANCIU, mentor

The Terahertz Time-Domain Spectroscopy (THz-TDS) is an accurate method used to characterize the dielectric properties of materials in millimiter and sub-millimeter wave domain. When compared to the conventional FTIR measurement method, THz-TDS provides not only the spectral intensity, but also the intrinsic phase shifts of the propagating THz signal allowing the direct finding of the complex dielectric permittivity without the use of the Kramers–Kronig relations.

Commercial (teflon, alumina, sapphire, magnesium oxide, quartz, etc.) and laboratory-made (BaNd₂Ti₅O₁₄, Zr_0.8Sn_0.2TiO₄, BaZn_1/3Ta_2/3O₃, BaMg_1/3Ta_2/3O₃) microwave dielectrics were investigated by using Terahertz Time-Domain Spectroscopy (THz-TDS) technique. Bulk and thin/thick film dielectrics were obtained by using conventional solid-state reaction method, pulsed electron beam deposition (PED), and radiofrequency plasma beam assisted pulsed laser deposition (RF-PLD), respectively. X-ray diffraction and scanning electron microscopy were employed for structural and morphological characterization of the samples. The transmission spectra were recorded with an Aispec IRS-2000 Pro time-domain spectrometer (40 GHz – 7 THz) on parallel-plane samples. For some samples, several optical phonon modes below 100 cm^-1 were evidenced.

ISI Article

1. L. Nedelcu, N.B. Mandache, M.I. Toacsan, A.M. Vlaicu, M.G. Banciu, A. Ioachim, F. Gherendi, C.R. Luculescu, M. Nistor, Dielectric properties of Ba(Zn_1/3Ta_2/3)O₃ thin films on Pt-coated Si substrates, Thin Solid Films 522 (2012) 112-116.
2. L. Nedelcu, N.D. Scarisoreanu, C. Chirila, C. Busuioc, M.G. Banciu, S.I. Jinga, M. Dinescu, Structural and dielectric properties of Ba(X_1/3Ta_2/3)O₃ thin films grown by RF-PLD, Applied Surface Science 278 (2013) 158-161.

Papers presented an International Conferences

1. L. Nedelcu, N. D. Scarisoreanu, C. Dragoi, C. Busuioc, M. G. Banciu, S. Jinga, M. Dinescu, Dielectric properties of Ba(X_1/3Ta_2/3)O₃ thin films grown by RF-PLD, E-MRS 2012 Spring Meeting, May 2012, Strassbourg, France.
2. L. Nedelcu, C. Busuioc, P. Ganea, M.G. Banciu,“Broadband dielectric spectroscopy of Ba(X_1/3Ta_2/3)O₃ complex perovskites, Electroceramics XIII, June 2012, Twente, Olanda.
3. L. Nedelcu, C. Busuioc, P. Ganea, M.G. Banciu, Terahertz spectroscopy of low-loss microwave dielectrics, ISAF ECAPD PFM 2012, July 2012, Aveiro, Portugal.
4. L. Nedelcu, C. Busuioc, M.G. Banciu, Terahertz time-domain spectroscopy of low-loss microwave ceramics, International Conference on Advanced Materials, August 2012, Brasov, Romania.
5. L. Nedelcu, C. Busuioc, M.G. Banciu, R. Ramer, Ba(X_1/3Ta_2/3)O₃ complex perovskites for microwave and millimeter wave applications, Proceedings of the 35th International Semiconductor Conference, CAS 2012, Sinaia, Romania, vol. 2 (2012) 303-306.
6. L. Nedelcu, N. D. Scarisoreanu, M. G. Banciu, M. Dinescu, Terahertz time-domain spectroscopy of Ba(Mg_1/3Ta_2/3)O₃ thick films, E-MRS 2013 Spring Meeting, May 2013, Strassbourg, France.
7. L. Nedelcu, C. Busuioc, M.G. Banciu, H.V. Alexandru, Terahertz properties of barium tantalate-based microwave dielectrics, 13^th International Balkan Workshop on Applied Physics, July 2013, Constanta, Romania.
8. L. Nedelcu and M.G. Banciu, Low-loss microwave dielectrics: synthesis, properties, and applications, 13^th International Balkan Workshop on Applied Physics, July 2013, Constanta, Romania (Invited Paper).

Dr. Liviu Nedelcu

Scientific researcher rank II

Laboratory of Complex Heterostructures and Multifunctional Materials

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

nedelcu@infim.ro