Temperature Dependences of Dielectric, Elastic and Piezoelectric Properties of KIO₃Single Crystals Associated with the Successive Phase Transitions

Abstract

Pottasium iodate, KIO 3 , belongs to the perovskite structure and undergoes successive phase transitions at T 1 = 212 • C, T 2 = 72.5 • C, T 3 = −15 • C, T 4 = −160 • C and T 5 = −240 • C, respectively. The temperature dependences of the dielectric, elastic and piezoelectic properties have been measured in the temperature range from −263 • C to 330 • C. The superionic conductivity was found in the temperature range above T 2 . Pronounced dielectric dispersions in the frequency range below 10 kHz were observed around −160 • C and −240 • C and the data were analyzed by fitting to the Davidson-Cole and Havriliak-Negami dispersion formulas, respectively. Both dielectric anomalies are ascribed to the taional glass-transitions. The piezoelectric and elastic properties have been investigsated by the resonance-antiresonance method. The piezoelectric and elastic anomalies were observed at T 2 and T 3 .Pottasium iodate, KIO 3 , is one of the most facinating member of the perovskite family owing to its non-linerar optical properites. 1) It undergoes successive phase transitions at T 1 = 212 • C, T 2 = 72.5 • C, T 3 = −15 • C and T 4 = −160 • C and T 5 = −240 • C, respectively, and is ferroelectric in all phases below 212 • C. 2) The phases are denoted here I, II, III, IV, V and VI-phases in decending order of the temperature.It has been reported that the space group in each phase is R3m(C 5 3v ) (T > T 1 ), Cm(Cs 3 ) (T 1 > T > T 2 ), and P1(C 1 1 ) (T 2 > T > T 3 ), respectively.3) The results of structural studies on KIO 3 until 1971 were summarized by Crane. 4) The structural details of the I-, II-and III-phases and their relation to the cubic prototype were discussed by Hamid. 2) The structural changes induced by the transitions at T 3 = −15 • C, T 4 = −160 • C and T 5 = −240 • C are not yet known. The phase transition at T 5 was found in the present investigastion. The phase transition at 130 • C reported by several authors is still questionable. 4)Investigations on the physical properties such as dielectric, 2, 5) elelctro-optical, 6, 7) piezoelectric properties, 6, 7) NQR 2) and Raman scatterng experiments 8, 9) of KIO 3 have been reported. Although much data have been reported especially on the temperature dependences of dielectric constants, still there has been some discrepancies between them. The ferroelectric properties of KIO 3 crystals at the successive phase transitions have been investigated in detail by Herlach 2) and Helg, 5) however, the behavior of KIO 3 has not been fully understood. Systematic measurements on the physical properties of KIO 3 have been required to understand the origin of the as 267 successive phase trnsitions.In this paper, dielectric, elastic and piezoelectric measurements have been performed in the temperature range between −263 • C and 330 • C and the mechanism of the successive phase transition has been investigated. §2. ExperimentalThe KIO 3 single crystals used in our experiment were grown from the aqueous solution containg KIO 3 and HIO 3 by the temperature lowering method. 10, ...

EXAFS study of phase transitions in KIO3

“…In addition, one should notice that the anomalous behavior appears in the DW factor for the PDFs of I-O(2) and I-I around 50 K that is near the phase transition temperature, TV VI 33 K. The phase transition at TV VI is considered as a glass transition whose transition temperature is diffused over the wide temperature range. Therefore, the anomaly in the DW factor should be contributed from the glass transition at TV VI, associated with the reorientational freezing of IO 3 molecules revealed from the dielectric measurements (Maeda et al, 2000). The reorientational freezing of IO 3 molecules is expected to increase the spatial correlation between the neighboring IO 3 molecules, which causes the decrease in the DW factor.…”

“…In order to understand the mechanism of the phase transitions, we need to clarify structural changes on them. Recently, Maeda et al (2000) have intensively studied the dielectric, elastic and piezoelectric properties of KIO3, and reported the nature of orientational glass transitions at TIV V and TV VI. We also have investigated the phase transitions using X-ray diffraction and EXAFS measurements to obtain additional structural information.…”

Phase transitions in KIO3

“…At temperature increase the symmetry changes in the sequence triclinic III 345.6 K monoclinic II 485 K trigonal I. The existence of these three phases is confirmed by studies investigating the temperature evolution of physical properties such as nuclear quadrupole resonance, Raman spectroscopy, pyroelectricity, birefringence, dielectric, elastic and piezoelectric properties [1,[7][8][9][10].…”

Исследование фазовых переходов сегнетоэлектрика KIO-=SUB=-3-=/SUB=- в нанопористых матрицах на основе пленок Al-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=-

“…Согласно недавним исследованиям [12], KIO 3 является несобственным сегнетоэлектриком, который претерпевает пять фазовых переходов при температурах около 485 K (из фазы I в фазу II), 345.5 K (из фазы II в фазу III), 258 K (при охлаждении) / 263 K (при нагреве) (из фазы III в фазу IV), 113 K (из фазы IV в фазу V) и при 33 K (из фазы V в фазу VI). Кроме того, наблюдается аномалия при температуре 428 ± 2 K, соответствующая изменению типа проводимости и не относящаяся к структурному фазовому переходу [13].…”

“…Кристалл KIO 3 в фазе I обладает ромбоэдрической структурой с симметрией R3m и является сегнетоэлектриком с полярной исходной фазой [14]. Моноклинная фаза II обладает симметрией Pm и триклинная фаза III -симметрией P1 [12]. Низкотемпературные фазы KIO 3 также имеют триклинную структуру, а переходы III-IV и IV-V связаны лишь с незначительными изменениями в расположении атомов [12,15].…”