Extremely Low Lattice Thermal Conductivity and Point Defect Scattering of Phonons in Ag-doped (SnSe)_1–<i>x</i>(SnS)_<i>x</i> Compounds

Lin, Chan-Chieh,Lydia, R.,Yun, Jae Hyun,Lee, Ho Seong,Rhyee, Jong Soo American Chemical Society 2017 Chemistry of materials Vol.29 No.12

<P>Single crystalline SnSe has been reported to exhibit the high thermoelectric zT value of 2.6 at 923 K along the b-axis direction, due to its low thermal conductivity [Zhao, L. D.; et al. Nature 2014, 508, 373]. However, the strongly anisotropic properties of the orthorhombic structure degrade the thermoelectric performance of polycrystalline SnSe, resulting in a low zT of 0.6 and 0.8 for Ag- and Na-doped SnSe, respectively. Here, we prepared Ag0.01Sn0.99Se1-xSx (x = 0, 0.10, 0.15, 0.20, and 0.35) compounds by melting and hot press sintering. The compounds showed extremely low thermal conductivity (0.11 W m(-1) K-1 at 825 K for x = 0.15). Using transmission electron microscopy images, we found that SnS alloying induced numerous nanoscale point defects. A Debye-Callaway model analysis supported the conclusion that the extremely low lattice thermal conductivity could be attributed to the point defect scattering of phonons. This resulted in a high zT of 1.67 at 823 K for the x = 0.15 sample, which is the state-of-the-art zT value for polycrystalline SnSe. Because the compounds are based on the environmentally friendly and cheap materials Sn, Se, and S, they make promising candidates for thermoelectric applications.</P>

Enhancement of Thermoelectric Performances in a Topological Crystal Insulator Pb_0.7Sn_0.3Se via Weak Perturbation of the Topological State and Chemical Potential Tuning by Chlorine Doping

Lin, Chan-Chieh,Kim, Gareoung,Ginting, Dianta,Ahn, Kyunghan,Rhyee, Jong-Soo American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.13

<P>Topological insulators generally share commonalities with good thermoelectric (TE) materials because of their narrow band gaps and heavy constituent elements. Here, we propose that a topological crystalline insulator (TCI) could exhibit a high TE performance by breaking its crystalline symmetry and tuning the chemical potential by elemental doping. As a candidate material, we investigate the TE properties of the Cl-doped TCI Pb<SUB>0.7</SUB>Sn<SUB>0.3</SUB>Se. The infrared absorption spectra reveal that the band gap is increased from 0.055 eV for Pb<SUB>0.7</SUB>Sn<SUB>0.3</SUB>Se to 0.075 eV for Pb<SUB>0.7</SUB>Sn<SUB>0.3</SUB>Se<SUB>0.99</SUB>Cl<SUB>0.01</SUB>, confirming that the Cl doping can break the crystalline mirror symmetry of a TCI Pb<SUB>0.7</SUB>Sn<SUB>0.3</SUB>Se and thereby enlarge its bulk electronic band gap. The topological band inversion is confirmed by the extended X-ray absorption fine structure spectroscopy, which shows that the TCI state is weakened in a chlorine <I>x</I> = 0.05-doped compound. The small gap opening and partial linear band dispersion with massless and massive bands may have a high power factor (PF) for high electrical conductivity with an enhancement of the Seebeck coefficient. As a result, Pb<SUB>0.7</SUB>Sn<SUB>0.3</SUB>Se<SUB>0.99</SUB>Cl<SUB>0.01</SUB> shows a considerably enhanced <I>ZT</I> of 0.64 at 823 K, which is about 1200% enhancement in <I>ZT</I> compared with that of the undoped Pb<SUB>0.7</SUB>Sn<SUB>0.3</SUB>Se. This work demonstrates that the optimal n-type Cl doping tunes the chemical potential together with breaking the state of the TCI, suppresses the bipolar conduction at high temperatures, and thereby enables the Seebeck coefficient to increase up to 823 K, resulting in a significantly enhanced PF at high temperatures. In addition, the bipolar contribution to thermal conductivity is effectively suppressed for the Cl-doped samples of Pb<SUB>0.7</SUB>Sn<SUB>0.3</SUB>Se<SUB>1-<I>x</I></SUB>Cl<SUB><I>x</I></SUB> (<I>x</I> ≥ 0.01). We propose that breaking the crystalline mirror symmetry in TCIs could be a new research direction for exploring high-performance TE materials.</P> [FIG OMISSION]</BR>

High thermoelectric performance and low thermal conductivity in K-doped SnSe polycrystalline compounds

Chan-Chieh Lin,Dianta Ginting,김가령,안경한,이종수 한국물리학회 2018 Current Applied Physics Vol.18 No.12

SnSe single crystal showed a high thermoelectric zT of 2.6 at 923 K mainly due to an extremely low thermal conductivity 0.23Wm−1 K−1. It has anisotropic crystal structure resulting in deterioration of thermoelectric performance in polycrystalline SnSe, providing a low zT of 0.6 and 0.8 for Ag and Na-doped SnSe, respectively. Here, we presented the thermoelectric properties on the K-doped KxSn1−xSe (x=0, 0.1, 0.3, 0.5, 1.5, and 2.0%) polycrystals, synthesized by a high-temperature melting and hot-press sintering with annealing process. The Kdoping in SnSe efficiently enhances the hole carrier concentration without significant degradation of carrier mobility. We find that there exist widespread Se-rich precipitates, inducing strong phonon scattering and thus resulting in a very low thermal conductivity. Due to low thermal conductivity and moderate power factor, the K0.001Sn0.999Se sample shows an exceptionally high zT of 1.11 at 823 K which is significantly enhanced value in polycrystalline compounds.

High thermoelectric performance and low thermal conductivity in K-doped SnSe polycrystalline compounds

Lin, Chan-Chieh,Ginting, Dianta,Kim, Gareoung,Ahn, Kyunghan,Rhyee, Jong-Soo ELSEVIER 2018 CURRENT APPLIED PHYSICS Vol.18 No.12

<P><B>Abstract</B></P> <P>SnSe single crystal showed a high thermoelectric zT of 2.6 at 923 K mainly due to an extremely low thermal conductivity 0.23 W m<SUP>−1</SUP> K<SUP>−1</SUP>. It has anisotropic crystal structure resulting in deterioration of thermoelectric performance in polycrystalline SnSe, providing a low zT of 0.6 and 0.8 for Ag and Na-doped SnSe, respectively. Here, we presented the thermoelectric properties on the K-doped K<SUB>x</SUB>Sn<SUB>1−x</SUB>Se (x = 0, 0.1, 0.3, 0.5, 1.5, and 2.0%) polycrystals, synthesized by a high-temperature melting and hot-press sintering with annealing process. The K-doping in SnSe efficiently enhances the hole carrier concentration without significant degradation of carrier mobility. We find that there exist widespread Se-rich precipitates, inducing strong phonon scattering and thus resulting in a very low thermal conductivity. Due to low thermal conductivity and moderate power factor, the K<SUB>0.001</SUB>Sn<SUB>0.999</SUB>Se sample shows an exceptionally high zT of 1.11 at 823 K which is significantly enhanced value in polycrystalline compounds.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The zT value of polycrystalline SnSe remains relatively low value. </LI> <LI> K-doping in SnSe efficiently enhances the hole carrier concentration. </LI> <LI> There exist prevalent Se-rich precipitates in the SnSe matrix, resulting in a very low thermal conductivity. </LI> <LI> The K<SUB>0.001</SUB>Sn<SUB>0.999</SUB>Se sample shows an exceptionally high zT of 1.11 at 823 K. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Temperature-dependent thermal conductivity <I>κ</I> (a) and dimensionless figure-of-merit <I>zT</I> values for K<SUB>x</SUB>Sn<SUB>1-x</SUB>Se (x = 0.0, 0.1, 0.3, 0.5, 1.5, and 2.0 mol.%) compounds.</P> <P>[DISPLAY OMISSION]</P>

Thermoelectric properties in Fermi level tuned topological materials (Bi1−xSnx)2Te3

Chan‑Chieh Lin,손원혁,Lydia Rathnam,이종수 대한금속·재료학회 2018 ELECTRONIC MATERIALS LETTERS Vol.14 No.2

We investigated the thermoelectric properties of Sn-doped (Bi1−xSnx)2Te3 (x = 0, 0.1, 0.3, 0.5, and 0.7%) compounds,which is known as topological insulators. Fermi level tuning by Sn-doping can be justified by the n- to p-type transitionwith increasing Sn-doping concentration, as confirmed by Seebeck coefficient and Hall coefficient. Near x = 0.3 and 0.5%,the Fermi level resides inside the bulk band gap, resulting in a low Seebeck coefficient and increase of electrical resistivity. The magnetoconductivity with applying magnetic field showed weak antilocalization (WAL) effect for pristine Bi2Te3while Sn-doped compounds do not follow the WAL behavior of magneto-conductivity, implying that the topological surfaceDirac band contribution in magneto-conductivity is suppressed with decreasing the Fermi level by Sn-doping. This researchcan be applied to the topological composite of p-type/n-type topological materials by Fermi level tuning via Sn-doping inBi2Te3compounds.

Thermoelectric Properties and Chemical Potential Tuning by K- and Se-Coalloying in (Pb0.5Sn0.5)1-xKxTe0.95Se0.05

Dianta Ginting,Chan-Chieh Lin,Gareoung Kim,Song Yi Back,Bora Won,조현용,Jae Hyun Yun,Hyeon Seob So,Hosun Lee,Byung-Kyu Yu,Sung-Jin Kim,Jong-Soo Rhyee 대한금속·재료학회 2019 ELECTRONIC MATERIALS LETTERS Vol.15 No.3

Topological crystal insulator (TCI) and topological Dirac semimetals have topologically nontrivial surface and bulk state,respectively. The parent compound of Pb 0.5 Sn 0.5 Te exhibiting TCI band inversion has particle-hole symmetry owing to thegapless Dirac band implying a strong electron–hole bipolar compensation in Seebeck coeffi cient. We recently reported thatweak perturbation of TCI state can enhance thermoelectric performance signifi cantly due to highly dispersive and degeneratedenergy bands. It is a great interest that the further increase of chemical potential has benefi ciary to thermoelectric performancein the vicinity of topological phase transition. Here we investigate the thermoelectric properties of the co-doping eff ect by Kand Se in (Pb 0.5 Sn 0.5 ) 1− x K x Te 0.95 Se 0.05 ( x = 0.0, 0.005, 0.010, 0.015, 0.02) compounds. K-doping increases the band gap from0.15 eV (Pb 0.5 Sn 0.5 Te) to 0.21 eV ( x = 0.05) as well as increasing chemical potential resulting in the suppression of bipolardiff usion eff ect. In spite of the suppression of bipolar diff usion eff ect by K-doping, the power factor in K-doped compoundis decreased signifi cantly than the one of non-doped Pb 0.5 Sn 0.5 Te 0.95 Se 0.05 compound. It indicates that when we increasechemical potential further on the breaking of topological band inversion, the thermoelectric performance is deterioratedbecause the chemical potential resides far from the linear band dispersions which become conventional material. The ZTfor the K-doped (Pb 0.5 Sn 0.5 ) 1− x K x Te 0.95 Se 0.05 is obtained as 0.91 at 750 K for x = 0.017 which is increased as much as 99%comparing to the pristine compound Pb 0.5 Sn 0.5 Te but it is reduced value (51.5%) comparing to those of Pb 0.5 Sn 0.5 Te 0.95 Se 0.05compound. We believe that this research is valuable on the confi rmation that the weak perturbation of topological state andappropriate chemical potential tuning are important criteria in high thermoelectric performance.

Prognostic value of right pulmonary artery distensibility in dogs with pulmonary hypertension

I-Ping Chan,Min-Chieh Weng,Tung Hsueh,Yun-Chang Lin,Shiun-Long Lin 대한수의학회 2019 Journal of Veterinary Science Vol.20 No.4

The right pulmonary artery distensibility (RPAD) index has been used in dogs with pulmonary hypertension (PH) caused by heartworm infection, myxomatous mitral valve disease, or patent ductus arteriosus. We hypothesized that this index correlates with the tricuspid regurgitation pressure gradient (TRPG) assessed by echocardiography and could predict survival in dogs with PH secondary to various causes. To assess this hypothesis, the medical records of 200 client-owned dogs at a referral institution were retrospectively reviewed. The RPAD index and the ratios of acceleration time to peak pulmonary artery flow (AT) and to the ejection time of pulmonary artery flow (ET) were recorded for each dog. The owners were contacted for follow-up assessments. The findings indicated that the RPAD index was correlated with the TRPG (R2 = 0. 362, p < 0.001). The survival time was significantly shorter in dogs with an RPAD index ≤ 21% that were followed up for 3 months and in dogs with an RPAD index ≤ 24% that were followed up for 1 year. Thus, the RPAD index was correlated with the TRPG and could predict the clinical outcome in dogs with PH caused by various diseases. This index could be used to evaluate the severity of PH in dogs without tricuspid regurgitation.

2022 Taiwan clinical multicenter expert consensus and recommendations for thyroid radiofrequency ablation

Wei-Che Lin,Wen-Chieh Chen,Pei-Wen Wang,Yi-Chia Chan,Yen-Hsiang Chang,Harn-Shen Chen,Szu-Tah Chen,Wei-Chih Chen,Kai-Lun Cheng,Shun-Yu Chi,Pi-Ling Chiang,Chen-Kai Chou,Feng-Fu Chou,Shun-Chen Huang,Feng 대한초음파의학회 2023 ULTRASONOGRAPHY Vol.42 No.3

Radiofrequency ablation (RFA) is a minimally invasive management strategy that has been widely applied for benign and recurrent malignant thyroid lesions as an alternative to surgery in Taiwan. Members of academic societies for specialists in interventional radiology, endocrinology, and endocrine surgery collaborated to develop the first consensus regarding thyroid RFA in Taiwan. The modified Delphi method was used to reach a consensus. Based on a comprehensive review of recent and valuable literature and expert opinions, the recommendations included indications, pre-procedural evaluations, procedural techniques, post-procedural monitoring, efficacy, and safety, providing a comprehensive review of the application of RFA. The consensus effectively consolidates advice regarding thyroid RFA in clinical practice for local experts.

Enhancement of thermoelectric performance <i>via</i> weak disordering of topological crystalline insulators and band convergence by Se alloying in Pb_0.5Sn_0.5Te_{1 − x}Se_x

Ginting, Dianta,Lin, Chan-Chieh,Kim, Gareoung,Yun, Jae Hyun,Yu, Byung-Kyu,Kim, Sung-Jin,Ahn, Kyunghan,Rhyee, Jong-Soo The Royal Society of Chemistry 2018 Journal of Materials Chemistry A Vol.6 No.14

<P>Topological crystal insulators (TCIs) that have an even number of topologically protected Dirac bands driven by crystalline mirror symmetry have attracted much attention in condensed matter physics. Here, we demonstrate that a weak disordering in the topological crystalline state can enhance thermoelectric performance significantly due to highly dispersive band dispersion and high band degeneracy which guarantee high electrical mobility and a high Seebeck coefficient, respectively. When we perturb a crystalline mirror symmetry by Se-doping in TCI Pb0.5Sn0.5Te1 − xSex, the topological state becomes weak so that it eventually evolves the normal state. We experimentally prove the topological phase transition concerning Se concentration by X-ray Absorption Spectroscopy (XAS) and extended X-ray absorption Fine Structure (EXAFS) analysis. Small crystalline perturbation by Se doping (<I>x</I> = 0.05) significantly enhances thermoelectric performance due to the simultaneous enhancement of electrical conductivity and the Seebeck coefficient. Therefore, we report an exceptionally high <I>ZT</I> value of 1.9 at 800 K for the <I>x</I> = 0.05 compound which is a 313% enhancement of <I>ZT</I> compared with the pristine compound. This research proposes a new strategy for exploring high-performance thermoelectric materials by weak disordering of topological crystalline Dirac semimetals.</P>

Enhancement of Thermoelectric Performance in Na-Doped Pb_0.6Sn_0.4Te_{0.95-<i>x</i>}Se_<i>x</i>S_0.05 via Breaking the Inversion Symmetry, Band Convergence, and Nanostructuring by Multiple Elements Doping

Ginting, Dianta,Lin, Chan-Chieh,Rathnam, Lydia,Kim, Gareoung,Yun, Jae Hyun,So, Hyeon Seob,Lee, Hosun,Yu, Byung-Kyu,Kim, Sung-Jin,Ahn, Kyunghan,Rhyee, Jong-Soo American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.14

<P>Topological insulators have attracted much interest in topological states of matter featuring unusual electrical conduction behaviors. It has been recently reported that a topological crystalline insulator could exhibit a high thermoelectric performance by breaking its crystal symmetry via chemical doping. Here, we investigate the multiple effects of Na, Se, and S alloying on thermoelectric properties of a topological crystalline insulator Pb<SUB>0.6</SUB>Sn<SUB>0.4</SUB>Te. The Na doping is known to be effective for breaking the crystalline mirror symmetry of Pb<SUB>0.6</SUB>Sn<SUB>0.4</SUB>Te. We demonstrate that simultaneous emergence of band convergence by Se alloying and nanostructuring by S doping enhance the power factor and decrease lattice thermal conductivity, respectively. Remarkably, the high power factor of 22.3 μW cm<SUP>-1</SUP> K<SUP>-2</SUP> at 800 K is achieved for Na 1%-doped Pb<SUB>0.6</SUB>Sn<SUB>0.4</SUB>Te<SUB>0.90</SUB>Se<SUB>0.05</SUB>S<SUB>0.05</SUB> mainly due to a relatively high Seebeck coefficient via band convergence by Se alloying as well as the suppression of bipolar conduction at high temperatures by the increase of energy band gap. Furthermore, the lattice thermal conductivity is significantly suppressed by PbS nanoprecipitates without deteriorating the hole carrier mobility, ranging from 0.80 W m<SUP>-1</SUP> K<SUP>-1</SUP> for Pb<SUB>0.6</SUB>Sn<SUB>0.4</SUB>Te to 0.17 W m<SUP>-1</SUP> K<SUP>-1</SUP> at 300 K for Pb<SUB>0.6</SUB>Sn<SUB>0.4</SUB>Te<SUB>0.85</SUB>Se<SUB>0.10</SUB>S<SUB>0.05</SUB>. As a result, the synergistically combined effects of breaking the crystalline mirror symmetry of topological crystalline insulator, band convergence, and nanostructuring for Pb<SUB>0.6</SUB>Sn<SUB>0.4</SUB>Te<SUB>0.95-<I>x</I></SUB>Se<SUB><I>x</I></SUB>S<SUB>0.05</SUB> (<I>x</I> = 0, 0.05, 0.1, 0.2, and 0.95) give rise to an impressively high <I>ZT</I> of 1.59 at 800 K for <I>x</I> = 0.05. We suggest that the multiple doping in topological crystalline insulators is effective for improving the thermoelectric performance.</P> [FIG OMISSION]</BR>