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XPS studies of the ferroelectric potassium lithium niobate crystal
Byeong-Eog Jun,Yoon-Hwae Hwang,Chung-Sik Kim,Hyung-Kook Kim,Jong-suk Chae,Jung-Nam Kim 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.46 No.1
Ar+-ion-sputtered surface of KLN crystal was studied by X-ray photoelectron spectroscopy in order to investigate the oxidation states and chemical environments of K, Li, Nb and O ions. As Ar+-sputtering time increased, the decreasing binding energy of Nb 3d and the peak broadening of mixed Nb 4s and Li 1s (namely Nb* 4s) levels were observed. Also, the binding-energy dierence between O 1s and Nb* 4s increased as Ar+-ion-sputtering time increased. The broad peak of Nb* 4s was considered to be related to the site occupancy of Li ion in A1 and C in tetragonal tungsten-bronze structure.
Jun, Byeong-Eog,Kim, Sas Byul,Li, Guojie,Chun Choi, Byung,Kee Moon, Byung,Hyun Jeong, Jung Royal Swedish Academy of Sciences 2010 Physica scripta Vol.2010 No.t139
<P>Alkaline niobate <I>A</I>NbO<SUB>3</SUB> (<I>A</I>=K, Li and Na) ceramics were fabricated into the composites of K<SUB>0.5</SUB>Na<SUB>0.5</SUB>NbO<SUB>3</SUB> (KNN) and NaK<SUB>2</SUB>Li<SUB>2</SUB>Nb<SUB>5</SUB>O<SUB>15</SUB> (NKLN) phases. The NKLN phase was composed of completely filled tetragonal tungsten-bronze and LiNbO<SUB>3</SUB> structures. The (1−<I>x</I>)KNN–(<I>x</I>/5)NKLN composite ceramics displayed alloy effects with changing <I>x</I>. The NKLN phase was expected to be solidified into the KNN phase through the liquidus–solidus curve of the (1−<I>x</I>)KNN–(<I>x</I>/5)NKLN composite ceramics. The (1−<I>x</I>)KNN–(<I>x</I>/5)NKLN composite ceramics showed the ferroelectric distortions with orthorhombic symmetry. We discussed the ferroelectric and dielectric properties of the (1−<I>x</I>)KNN–(<I>x</I>/5)NKLN composite ceramics.</P>
Dielectric properties of the near stochiometric KLN crystal in the ferroelectric Curie range
Yoon-Hwae Hwang,Byeong-Eog Jun,Chungsik Kim,Dong-Jin Kim,Hyung-Kook Kim,Jung-Nam Kim 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.46 No.1
The dielectric constants of near-stoichiometric potassium lithium niobate (K2:83Li1:84Nb5:33O15:66 , KLN43) crystal in the frequency range from 100 Hz to 1 MHz showed a dielectric anomaly at maximum temperatures around Tmax = 510 C. At low frequencies, ranging from 100 Hz to 10 kHz, the dielectric maximum temperature Tmax shifted to higher temperature as the frequency increased in the Curie range. The impedance Cole-Cole plot in the Curie range could betted by the complex nonlinear least squares (CNLS) method with two parallel Rcircuits in series: Z(!) = R1=[1 + (i!)n11]+R2=[1 + (i!)n22], where 1 and 2 are the relaxation times,1;2 = R1;2C1;2. The universal capacitance Ce= C(i!)n1 was applied for each RCecircuit. This observation suggests that the universal dynamic response of KLN43 crystal in the Curie rangewas the superposition of the low-frequency dispersion (LFD) due to the mobile charge carriers and to the rotational dielectric relaxation mechanism in the dipolar regions.
Diffuse Phase Transition of Potassium Lithium Niobate Single Crystals Probed by Brillouin Scattering
고재현,Do Han Kim,Seiji Kojima,Byeong-Eog Jun,황윤홰 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.2
A Brillouin light scattering study has been carried out on tungsten-bronze K5.80Li3.82Nb10.12O30 (KLN-1) single crystals, which exhibited diffuse ferroelectric phase transitions at Tc 700 K. Polarized central peaks (CPs) were observed in the paraelectric phase, indicating the existence of precursor polar clusters. The relaxation time, estimated from the width of the CP, showed a substantial increase at T Tc + 100 K, at which the polar clusters seemed to become more correlated and longer lived than at higher temperatures, similar to the case of the most typical uniaxial relaxor, (Sr0.61Ba0.39)5Nb10O30 (SBN-61). The temperature dependence of the relaxation time showed a different behavior from that of the typical order-disorder-type ferroelectrics, which has been ascribed to the intrinsic disorder of the unfilled tungsten-bronze structure and the resulting quenched random electric fields. A Brillouin light scattering study has been carried out on tungsten-bronze K5.80Li3.82Nb10.12O30 (KLN-1) single crystals, which exhibited diffuse ferroelectric phase transitions at Tc 700 K. Polarized central peaks (CPs) were observed in the paraelectric phase, indicating the existence of precursor polar clusters. The relaxation time, estimated from the width of the CP, showed a substantial increase at T Tc + 100 K, at which the polar clusters seemed to become more correlated and longer lived than at higher temperatures, similar to the case of the most typical uniaxial relaxor, (Sr0.61Ba0.39)5Nb10O30 (SBN-61). The temperature dependence of the relaxation time showed a different behavior from that of the typical order-disorder-type ferroelectrics, which has been ascribed to the intrinsic disorder of the unfilled tungsten-bronze structure and the resulting quenched random electric fields.
Kim, Su Jae,Cha, Su Young,Kim, Ji Young,Shin, Jong Moon,Cho, Yong Chan,Lee, Seunghun,Kim, Won-Kyung,Jeong, Se-Young,Yang, Y. S.,Cho, Chae Ryong,Choi, H. W.,Jung, Myung-Hwa,Jun, Byeong-Eog,Kwon, Ki-Yon American Chemical Society 2012 The Journal of Physical Chemistry Part C Vol.116 No.22
<P>There have been many studies of ferromagnetism in ZnCoO, and the results have been controversial. Secondary phases, such as Co oxides and Co metal clusters, in ZnCoO are easily produced during treatment, but the formation conditions are not well understood. We fabricated samples under hydrogen-injection conditions at different heat-treatment temperatures and examined the conditions by using synchrotron X-ray analysis under which Co<SUB>3</SUB>O<SUB>4</SUB> appeared or was transformed into Co metal. We investigated the transforming process of the ferromagnetic origin from intrinsic to extrinsic nature via intermediate region competition by Co–H–Co and Co metal cluster and suggest conditions that induce ferromagnetic spin ordering in ZnCoO due to Co–H–Co complexes through hydrogen mediation.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2012/jpccck.2012.116.issue-22/jp300536w/production/images/medium/jp-2012-00536w_0010.gif'></P>