Lithuanian Journal of Physics article / Lietuvos fizikos žurnalo straipsnis

BROADBAND AND INFRARED SPECTROSCOPY OF Ag_0.98Li_0.02NbO₃ CERAMICS
Edita Palaimienė^a, Jan Macutkevič^b, Jūras Banys^a, Irena Gruszka^c, and Antoni Kania^c
^aInstitute of Applied Electrodynamics and Telecommunications, Vilnius University, Saulėtekio 3, 10257 Vilnius, Lithuania
^bCenter for Physical Sciences and Technology, Saulėtekio 3, 10257 Vilnius, Lithuania
^cInstitute of Physics, University of Silesia in Katowice, ul. 75 Pułku Piechoty 1, PL-41-500 Chorzów, Poland
Email: edita.palaimiene@ff.vu.lt

Received 17 September 2020; revised 28 October 2020; accepted 3 November 2020

The dielectric properties of Ag_0.98Li_0.02NbO₃ (ALN2) ceramics were investigated in a broad frequency range (20 Hz – 60 THz). The dielectric spectra of ALN2 ceramics are mainly impacted by electrical conductivity at higher temperatures (above 400 K) and low frequencies (below 100 Hz), ferroelectric domains below ferroelectric phase transition temperature T_c = 330 K and at low frequencies (below 1 MHz), and contribution of the soft ferroelectric mode, the frequency of which is below 50 cm^–1. All phononic modes are slightly temperature dependent, thus confirming the influence of Ag, O and Li ions dynamics on the phase transitions. However, the most important contribution to the dynamics of phase transition is made by Nb ions. Ceramics exhibits a huge value of dielectric permittivity and relatively low losses in a microwave frequency range (ε΄ ≈ 250 and ε˝ ≈ 20 at 10 GHz and room temperature), indicating that it is suitable for various microwave dielectric applications.

Keywords: ceramics, spectroscopy, phonons, ferroelectric
PACS: 77.84.Cg, 78.47.-p, 63.20.dd, 77.84.-s

PLAČIAJUOSTĖ Ag_0,98Li_0,02NbO₃ KERAMIKŲ DIELEKTRINĖ IR INFRARAUDONOJI SPEKTROSKOPIJA
Edita Palaimienė^a, Jan Macutkevič^b, Jūras Banys^a, Irena Gruszka^c, Antoni Kania^c

^aVilniaus universiteto Taikomosios elektrodinamikos ir telekomunikacijų institutas, Vilnius, Lietuva
^bFizinių ir technologijos mokslų centras, Vilnius, Lietuva
^cKatovicų Silezijos universiteto Fizikos institutas, Chožuvas, Lenkija

Bešvinė pjezoelektrinė niobato sistemos medžiaga galėtų būti alternatyva jau žinomoms ir naudojamoms pjezoelektrinėms medžiagoms. Viena iš tokių feroelektrinių medžiagų yra perovskito struktūros sidabro niobatas AgNbO₃ (AN). Sidabro niobato keramika yra feroelektrikas kambario temperatūroje. Tyrimais nustatyta, kad didinant ličio koncentraciją sidabro niobato junginyje feroelektrinio fazinio virsmo temperatūra taip pat didėja. Šiame darbe publikuojami Ag_0,98Li_0,02NbO₃(ALN2) dielektrinių ir IR tyrimų rezultatai. Tyrimai atlikti plačiajuostės dielektrinės ir IR spektroskopijų metodais 20 Hz – 60 THz dažnių diapazone esant 140–500 K temperatūrai. ALN2 keramikos dielektriniams spektrams daugiausia įtakos turi elektrinis laidumas (aukštesnei temperatūrai (per 400 K) ir žemiems dažniams (žemiau 100 Hz)), feroelektriniai domenai (žemiau T_c = 330 K, esant žemiems dažniams (žemiau 1 MHz)) ir minkštos feroelektrinės modos, kurios dažnis yra mažesnis nei 50 cm^–1, įtaka. Ag ir O jonų dinamika turi įtakos faziniams virsmams, tai lemia fononines modas, kurios šiek tiek priklauso nuo temperatūros. Svarbiausią indėlį į fazinių virsmų dinamiką turi Nb jonai. ALN keramika turi didžiulę dielektrinės skvarbos vertę ir santykinai mažus nuostolius mikrobangų dažnių diapazone (ε΄ ≈ 250 ir ε˝ ≈ 20 esant 10 GHz ir kambario temperatūrai).

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