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Elastic Anomalies Associated with the Antiferroelectric Phase Transitions of PbHfO3 Single Crystals
고재현,Krystian Roleder,Andrzej Majchrowski,Annette Bussmann-Holder 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.64 No.8
The temperature dependence of the elastic properties of antiferroelectric PbHfO3 was investigatedby using Brillouin scattering. The two structural phase transitions of antiferroelectricantiferroelectric-paraelectric phases were clearly identified from the discontinuous changes in theacoustic mode frequencies and the hypersonic damping. The substantial softening of the modefrequency, along with the remarkable increase in the acoustic damping observed in the paraelectricphase, indicated the formation of precursor noncentrosymmetric (polar) clusters and their couplingto the acoustic waves. This was corroborated by the observation of quasi-elastic central peaks,the intensity of which grew upon cooling toward the Curie point. The obtained relaxation timeexhibited a slowing-down behavior, suggesting that the dynamics of the precursor clusters becamemore sluggish on approaching the phase transition temperature.
홍정택,이병완,고재현,Irena Jankowska-Sumara,Maria Podgórna,Andrzej Majchrowski 한국물리학회 2018 Current Applied Physics Vol.18 No.6
The phase transition sequence of a PbHf0.7Sn0.3O3 single crystal was investigated by using Brillouin spectroscopy. The longitudinal acoustic mode showed three distinct changes at ∼370 K, ∼455 K and ∼495 K which corresponded to the antiferroelectric 1 → antiferroelectric 2 → intermediate → paraelectric phase transitions upon heating. The paraelectric phase was characterized by softening acoustic mode, increasing acoustic damping and the appearance of quasielastic central peaks which were observed upon approaching the phase transition temperature. The relaxation times derived from the acoustic mode anomalies and the central peak were consistent with each other and showed a slowing-down behavior. These precursor phenomena were attributed to the polar clusters having broken inversion symmetry. The substitution of Hf with Sn induced a very soft intermediate phase between the paraelectric and the antiferroelectric phases, where the longitudinal acoustic mode exhibited the lowest mode frequency along with substantially high acoustic damping. The transverse acoustic mode, which was observed in the two antiferroelectric phases, did not appear in the intermediate phase. These results indicated that the average symmetry of the intermediate phase may be cubic consisting of fine ferroelastic domains.
Hong, Jung-Taek,Lee, Byoung Wan,Ko, Jae-Hyeon,Jankowska-Sumara, Irena,Podgó,rna, Maria,Majchrowski, Andrzej ELSEVIER 2018 Current Applied Physics Vol.18 No.6
<P><B>Abstract</B></P> <P>The phase transition sequence of a PbHf<SUB>0.7</SUB>Sn<SUB>0.3</SUB>O<SUB>3</SUB> single crystal was investigated by using Brillouin spectroscopy. The longitudinal acoustic mode showed three distinct changes at ∼370 K, ∼455 K and ∼495 K which corresponded to the antiferroelectric 1 → antiferroelectric 2 → intermediate → paraelectric phase transitions upon heating. The paraelectric phase was characterized by softening acoustic mode, increasing acoustic damping and the appearance of quasielastic central peaks which were observed upon approaching the phase transition temperature. The relaxation times derived from the acoustic mode anomalies and the central peak were consistent with each other and showed a slowing-down behavior. These precursor phenomena were attributed to the polar clusters having broken inversion symmetry. The substitution of Hf with Sn induced a very soft intermediate phase between the paraelectric and the antiferroelectric phases, where the longitudinal acoustic mode exhibited the lowest mode frequency along with substantially high acoustic damping. The transverse acoustic mode, which was observed in the two antiferroelectric phases, did not appear in the intermediate phase. These results indicated that the average symmetry of the intermediate phase may be cubic consisting of fine ferroelastic domains.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We measure the elastic properties of PbHf<SUB>0.7</SUB>Sn<SUB>0.3</SUB>O<SUB>3</SUB> single crystals. </LI> <LI> The acoustic anomalies related the phase transition are determined. </LI> <LI> The effect of Sn substitution on the elastic property is determined. </LI> </UL> </P>