UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS

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Conference: Bucharest University Faculty of Physics 2016 Meeting


Section: Solid State Physics and Materials Science


Title:
Testing of Mg4Nb2O9 Ceramics for Space Applications


Authors:
Laura MIHAI (1), Andrei STACALIE (1), Dan SPOREA (1), L. NEDELCU (2), C. D. GEAMBASU (2), M. G. BANCIU (2), V. GHENESCU (3), T. PREDA (3), M. M. GUGIU (4)


Affiliation:
1) National Institute for Laser, Plasma and Radiation Physics, Magurele, Romania

2) National Institute of Materials Physics, Magurele, Romania

3) Institute of Space Science, Magurele, Romania

4) Horia Hulubei National Institute of Physics and Nuclear Engineering,

Magurele, Romania


E-mail
laura.mihai@inflpr.ro


Keywords:
Mg4Nb2O9, ceramics, microwave device, THz spectroscopy, THz imaging, vibration testing, proton radiation


Abstract:
The goal of the reported investigation was to test low-loss Mg4Nb2O9 (MNO) dielectrics for their possible use in space microwave devices such as filters, oscillators, antennas, etc. These materials were prepared by using a conventional ceramic route from high purity MgO and Nb2O5 oxides. Their qualification for the inclusion in 'space equipments' was evaluated by exposing them to protons and by subjecting them to vibration tests. Prior to and following these tests the MNO samples were measured in microwaves with Hakki-Coleman method and were also investigated by THz imaging using TPS3000 THz spectrometer from TeraView, transmittance and reflectance imaging module (RIM). The non-irradiated sample refractive index was around 3.8 in THz range. Proton irradiation was performed at IFIN’s 3 MV Cockcroft-Walton Tandetron accelerator. The ceramic sample has been exposed to protons with 500 keV energy and 1012 particles/cm2 fluency. Non-irradiated ceramics had dielectric constant values of about 13.4 and losses lower than 2.4x10 -4 at 8.4 GHz. Within the detection limit, no changes of the dielectric constant were noticed for proton-irradiated samples. On the other hand, the radiation-induced defects lead to a10 % increase of the microwave dielectric loss. Vibration tests were run at INFLPR using a shock and vibration system type “ES-6-230” from Dongling Technologies. The testing conditions followed the acceptance norms for horizontal and vertical induced vibrations: frequencies ranging from 10 to 50 Hz at a level of 0.124 m/s velocity and from 50 to 2000 Hz frequency at 4.0 g, both with a sweep rate of 4 octave / minute. Sinusoidal and random vibration test levels were conducted. The testing conditions followed REXUX requirements for all flight equipment. Using THz imaging we were able to investigate the sample defects and uniformity in depth before and after vibrations tests and no noticeable changes were detected.


Acknowledgement:
The authors acknowledge the financial support of the Romanian Space Agency under project 85/2013 and of the Romanian Authority for Scientific Research under grant PN-II-PT-PCCA-2013-4-0967 and program NUCLEU 2016.