Month: September 2017

The symposium lasted for three days.  On the first day, we had session on thin film and nano sheets fabricated by various methods.  After the poster session (about 32 posters) for 2 hours, there was hydrothermal synthesis session.  On the second day, we first concentrated on low-thermal-conductive and thermoelectric materials, materials design, YBCO and Perovskite related materials.  Last session was on battery material.  On the third day, photoelectrochemical and magnetic properties of various materials were discussed.  One of the talks that attracted audience attention was on spinodal decomposition induced by magnetic field.  We find that there are areas related to advanced ceramics and composites where we should work hard to maintain sustainable society.

A5-I01-005

Prof Neophytou described his method to determine if nanostructures can improve Seebeck Coefficient. In the simple model of electron filtering there is actually no improvement. depending on lambda_E there can be a modest improvement. need quantum reflections not tunneling. Avoid ionized impurity scattering. dislocation networks can increase power factor.

A5-O01-008

Teng Fang described computational efforts to find new p-type Half Heusler by looking for compounds with low effective mass. Calculations confirmed that 5d have lower effective mass than 4d transition metals. multiband effects are also calculated. Predicting RuTaSb as good TE materials.

A5-O01-009

H.Takaki TE transport properties (thermal and electrical) of Magnetic Semiconductor CuFeS2 is calculated. Fe doping lowers lattice thermal conductivity. lattice thermal conductivity is larger along a-axis than c=axis. predicts more dilute doping would make better zT.

Nonthermal Biocompatible Plasma (NBP) Sources and Their Nanoparticle Interaction Characteristics for Plasma Medicine

Eun Ha Choi of Kwangwoon University, Korea, gave an excellent keynote lecture in the oral session of Symposium C-5 in the morning session on September 1. He first presented plasma devices used in Plasma Bioscience Research Center of Kwangwoon University, e.g., nonthermal biocompatible plasma (NBP) Jet, dielectric barrier discharge (DBD) systems, and nanosecond pulsed plasma systems. He introduced plasma diagnostics for NBP jet and DBD systems, and measured various kinds of plasma parameters, such as electron temperature, electron density, radical density, excited nitrogen density, electrical discharge energy, vibration temperature, rotation temperature, and so on. As plasma initiated ultraviolet photolysis and transport, he explained reactive oxygen species (ROS) generation mechanism in extracellular and intracellular region. He also reported that plasma with PEG-coated gold nanoparticles sensitize glioma, suppress cellular transformation by inhibiting growth and epithelial mesenchymal transition (EMT).

Modification of Gene Expression of Plants Induced by Active Oxygen Species in Oxygen Plasma

Nobuya Hayashi of Kyushu University, Japan, gave a keynote lecture in the oral session of Symposium C-5 in the afternoon session on September 1. He presented the effects of oxygen plasma irradiation to plant seeds. He showed that 1. growth enhancement occurred and genes related to energy production were expressed, 2. growth enhanced effects had not passed onto next generations, and 3. genes involved in epigenetics were expressed. These results indicated that the growth enhancement effect due to plasma irradiation was induced by epigenetics. He was going to clarify the relationship between the growth enhancement effect and epigenetics

Keynote lecture scene by Prof. Choi.

Keynote lecture scene by Prof. Hayashi.

In the opening talk prof. Sdyder of Northwestern University reviewed the role of Fermi Surface Complexity Factor for Thermoelectric Materials giving a wide number of examples and state of the art of experiments an band structure calculations.

Prof. Oh of hanbat University (Korea) gave a complementary talk with instructive overview on Therthe effect of band structure modulation on thermoelectric properties.

In his invited talk entitled “Novel nitride an oxide thin-film materials for thermoelectrics” Per Eklund (Linkoping University) reported about a ten-year investigation of ScN systems. While the nitride itself has a very good power factor, its thermal conductivity was too large to make its ZT acceptable. Adding Cr resulted in a significant reduction of κ. Further improvement of ZT could be achieved through a systematic investigation of transition metals capable of forming stable solid solutions with ScN (either ordered or disordered). A likely reduction of the thermal conductivity could also be achieved by generating (Ti, W)N-(Sc, Al)N superlattices, but the nanostructure was found to be stable only up to 950 °C, limiting its applicability. In the second part of his talk, Eklund discussed his research on Ca₂Co₄O₉. Its laminar structure makes the material quite performing, and it was shown that thin films grown onto mica may be peeled off, leading to one of the few examples of flexible and self-sustaining inorganic thin films.

Gao Min (Cardiff University) ended the session with a keynote entitled “A high-throughput approach towards accelerated discovery of promising thermoelectric materials” where combinatorial methods were applied to quicken the exploratory research on new thermoelectrics. He focused on binary (and ternary) alloys. The aim of the wok was to reduce the enormous number of possible A_xB_y compounds to be tested in the search for high ZT. Using very simple element characteristics such as electronegativity and atomic weight, radius, and number, he could show how efficient TE materials cluster together. Although the method does not aim at pointing out which binary compound might have large ZT, it enabled the experimental investigator to discard binary (and ternary) compounds which do not qualify as good thermoelectrics. His analysis was supported by experiments carried out by laser melting that enabled the fast synthesis and characterization of a large number of binary compounds.

Prof. Mele of Muroran IT gave final remarks on the symposium A5 which was highly succesfull, with the highest number of presentations in the whole conference. All talks and posters were excellent and top-level research on thermoelectric was widely represented. Symposium A5 was enriched with AAT school (pre-event) and satellite workshop. There is strong intention to organize the thermoelectric symposium during IUMRS-ICAM 2019 in Nice.

Symposium No.: A5-101-011 （invited talk）  9:00-9:25

Title: Enclathration of simple and complex cations in phosphide thermoelectrics

Kirill Kovnir from University of California (Now he moved to the Iowa State University) presented the design and realization of new caged compounds of Phosphide Thermoelectrics. The chemical way to design these new phosphide materials, the synthesis as well as their thermoelectric properties and the approach aimed for enhanced electrical properties were introduced in detail. Kirill Kovnir and his collaborators started their research in caged compounds of Ba₈M₁₆P₃₀ (M=Cu and Au), which possessed a low lattice thermal conductivity of about 0.5 Wm^-1K^-1 or lower, a value very good for high thermoelectric performance. Further on, they continued to explore other caged compounds, such as BaNi₂P₄, SrNi₂P₄, Ba-Zn-Cu-P and Ba-Ge-Cu-P based system. The chemical bonds and coordination of elements are discussed in detail for more insight on the variation in thermoelectric properties. A high thermoelectric figure of merit of about 0.8 was achieved in the best compounds due to the improved electrical properties from chemical doping.

Title: Thermoelectric properties of new As-based compounds of Ba1-xKxZn2As2

Kunihiro Kihou from AIST, Japan and collaborators attempted to synthesize Zintle phase compound of K doped BaZn₂As₂ and investigated the thermoelectric properties. BaZn₂As₂ is the analogue of famous Zintl compound of CaAl₂Sb₂. This K doped BaZn₂As₂ compounds were prepared by the AIST tube method, which is suitable for handling materials with high reactivity. With the K doping, the resistivity and the Seebeck decreased, while the lattice thermal conductivity remained the similar value. Finally, the thermoelectric figure of merit ZT was increased from 0.2 to 0.7. This enhancement is mainly resulted from the much enhanced electrical properties.