Ultrasonic Study of the Li-induced Structural Phase Transition in K _{1− x} Li _x TaO ₃

Abstract

In order to clarify the nature of the possible structural changes taking place in K1−xLixTaO3 (KLT), we have performed an ultrasonic study of three KLT crystals with approximate Li concentrations, 1.5%, 3.5% and 5%. A step increase in the velocity and a corresponding attenuation anomaly clearly indicate structural changes occurring at 30 K, 55 K and 75 K, respectively. In the two higher-concentration crystals, the large magnitude of this change and the observation of thermal hysteresis signal a macroscopic structural transition with a first-order character. In the lower-concentration crystal, a 3 to 5 times smaller effect and the absence of a hysteresis are attributed to local structural distortions without long-range order. This interpretation agrees with the conclusion of a recent Raman study of the same crystals. It provides a direct physical test of this conclusion which was derived from selection rules.

Fluctuating defects in the incipient relaxorK1−xLixTaO3(x=Stock1, Gehring2, Xu3 et al. 2014Phys. Rev. B10290View full textAdd to dashboardCite

“…79) and also ultrasound measurements which probes the acoustic velocity in the limit as q approaches the zone center (Ref. 80).…”

Surface structure of lithium-doped potassium tantalate using helium atom scattering

“…The cubic/paraelectric to tetragonal phase transitions for 1.5% Li, 3.5% Li, and 5% Li are at 30, 55, and 75 K, respectively. 9 Sample temperatures in the experiments in this paper were kept well above any of the known transition temperatures and, hence, the bulk samples were presumed to be in the cubic/paraelectric phase.…”

“…The bulk structures of several oxide perovskites relevant to this work have been investigated extensively. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] Helium atom scattering (HAS) experiments have been reported from this laboratory on the surface structure and dynamics of the perovskites potassium tantalate (KT) 22,23 and potassium tantalate doped with niobium (KTN) over a range of concentrations. [24][25][26] A theoretical study of the surface of KT has also been reported.…”

Non Ergodic Aging in an Orientational Glass

“…Typical data of the real and imaginary parts of the dielectric constant [3] at several frequencies and of the real and imaginary parts of the elastic constant [4] also at various frequencies are shown as a function of temperature for two KLT samples, one with x = 0.015 (figure 1) and the other with x = 0.05 (figure 2).…”