Correlation of Electrical Properties and Acoustic Loss in Single Crystalline Lithium Niobate-Tantalate Solid Solutions at Elevated Temperatures

Abstract

Electrical conductivity and acoustic loss Q−1 of single crystalline Li(Nb,Ta)O3 solid solutions (LNT) are studied as a function of temperature by means of impedance spectroscopy and resonant piezoelectric spectroscopy, respectively. For this purpose, bulk acoustic wave resonators with two different Nb/Ta ratios are investigated. The obtained results are compared to those previously reported for congruent LiNbO3. The temperature dependent electrical conductivity of LNT and LiNbO3 show similar behavior in air at high temperatures from 400 to 700 °C. Therefore, it is concluded that the dominant transport mechanism in LNT is the same as in LN, which is the Li transport via Li vacancies. Further, it is shown that losses in LNT strongly increase above about 500 °C, which is interpreted to originate from conductivity-related relaxation mechanism. Finally, it is shown that LNT bulk acoustic resonators exhibit significantly lower loss, comparing to that of LiNbO3.

‘Horror Vacui’ in the Oxygen Sublattice of Lithium Niobate Made Affordable by Cationic Flexibility

“…Originally, the same was also assumed for LiNbO 3 (LN), and most authors did not (and many still do not) have any doubts about simply postulating vacant oxygen sites (V O ) capable of trapping one or two electrons (F + and F-centers, respectively) in discussions of their experiments and proposed applications (see, e.g., [1,2]). The controversy about the availability of oxygen vacancies manifests in the reviews of Sánchez-Dena et al [3,4], is touched upon by some topical reviews [5,6], and is also closely related to the topics of other papers [7][8][9][10][11] of the present Special Issue, and deserves a clarifying discussion.…”

“…The authors attributed the final recombination step near 350 • C in near-sLN to the release of oxygen interstitials annihilating the oxygen vacancies. However, this temperature corresponds to the well-known starting temperature of first-stage thermal reduction governed by Li mobility, also identified in ionic conductivity studies (for references see [9]), while the onset of oxygen mobility of any kind is expected at substantially higher temperatures [20][21][22]. In fact, in the framework of the bipolaron scenario, there is also a straightforward explanation for the observed difference between slow and fast coloration processes near room-temperature: for the stability of the doubly recharged defect, a change in its charge-compensation is required, which can be provided by the time-and energyconsuming diffusion of cation vacancies away and back to the antisite.…”

“…Compared to compensation involving anion vacancies at larger costs [13,14], compensation only by cationic disorder requires no additional volume and leads to the observed larger density of cLN compared to sLN (stoichiometric LN) [15][16][17][18][19]. Another characteristic property of LN is the high mobility of Li + ions observable already at temperatures near 350 • C (see [9,[20][21][22] and references therein). It should be noted that LN is just an intermediary phase between Li 3 NbO 4 and LiNb 3 O 8 , considered as cathode and anode materials for lithium-ion batteries, respectively [23,24].…”

New Trends in Lithium Niobate: From Bulk to Nanocrystals

“…Electrical conductivity and acoustic loss of single crystalline Li(Nb,Ta)O 3 solid solutions (LNT) were studied as a function of temperature and compared to those in LN and LT crystals by Suhak et al [12]. The dominant transport mechanism in LNT in the range of 400-700 • C was identified as lithium-ion migration via lithium vacancies, as found in LN.…”

Local variations of the piezoelectric properties of an LiNb(1−x)Ta x O3 crystal

“…Piezoelectric materials have long been successfully used in a wide variety of applications. Recently, increased attention has been paid to the growth and study of ferroelectric crystals of the solid solutions of LiNb (1Àx) Ta x O 3 (Suhak et al, 2021;Ru ¨sing et al, 2016;Roshchupkin et al, 2020). This is due to, on the one hand, the wide range of applications of crystals of the LiNbO 3 -LiTaO 3 system edge compounds and, on the other hand, the possibility of varying the acoustic, piezoelectric and optical properties of crystals depending on the ratio of isomorphic cations in the range from LiTaO 3 to LiNbO 3 .…”