Phase Stability, Phase Transformations, and Reactive Phase Formation in Electronic Materials XVI: Phase Stability on Energy Materials
Sponsored by: TMS Functional Materials Division, TMS: Alloy Phases Committee
Program Organizers: Shih-kang Lin, National Cheng Kung University; Chao-hong Wang, National Chung Cheng University; Jae-Ho Lee, Hongik University; Ikuo Ohnuma, National Institute for Materials Science (NIMS); Chih-Ming Chen, National Chung Hsing University; Thomas Reichmann, Karlsruhe Institute of Technology; Yu Zhong, Florida International University; Shijo Nagao, Osaka University; Shien Ping Tony Feng, The University of Hong Kong; Yee-wen Yen, National Taiwan Univ of Science & Tech

Monday 8:30 AM
February 27, 2017
Room: 25A
Location: San Diego Convention Ctr

Session Chair: Yu Zhong, Florida International University; Thomas Reichmann, Karlsruhe Institute of Technology

8:30 AM  Invited
Phase Transformations at Thermoelectric-Metal Interfaces - Thermodynamic Modeling: Yong-Jie Hu1; Yi Wang1; Samad Firdosy2; Zi-Kui Liu1; Samad Firdosy2; Kurt Star2; Jean-Pierre Fleurial2; Vilupanur Ravi2; 1Pennsylvania State University; 2Jet Propulsion Laboratory/California Institute of Technology
    Thermodynamic modeling of the Yb-Mn-Sb-Ni quaternary system was carried out by a CALPHAD approach to understand the phase equilibrium at the interface between the semiconducting, thermoelectric Yb14MnSb11 (zintl) material and metallic nickel. The thermodynamic properties of the intermetallic compounds were investigated via a first-principles phonon approach. Five binary systems, i.e., YbNi, YbNi2, Yb2Ni3, YbNi5, and YbNi17, and four ternaries YbMn2Sb2, YbNiSb, MnNiSb and Yb14MnSb11 were studied. The thermodynamic properties of Yb14MnSb11, including the phonon density of state, heat capacity, entropy, thermal expansion and elastic moduli, were evaluated and compared with available experimental data. The thermodynamic properties of the Yb-Ni binary system were re-assessed based on first-principles thermochemical data and experimental data. A thermodynamic description of the Yb-Mn-Sb-Ni quaternary system developed by combining the previously modeled constituent binary systems and the calculated thermodynamic properties of the constituent ternary compounds will be presented along with relevant insights into the interfacial reactions.

9:00 AM  
Phase Transformations at Thermoelectric-Metal Interfaces – Experimental Analysis: Samad Firdosy1; Kurt Star1; Jean-Pierre fleurial1; Vilupanur Ravi2; Yong-Jie Hu3; Yi Wang3; Zi-Kui Liu3; 1Jet Propulsion Laboratory/California Institute of Technology; 2Jet Propulsion Laboratory/California Institute of Technology and Cal Poly Pomona, Pomona, Ca; 3Pennsylvania State University
    The Advanced Thermoelectric Couple development Task, as part of NASA’s Radioisotope Power Systems Program’s Thermoelectric Technology Development Project (TTDP), has developed several advanced high-temperature thermoelectric materials, including n-type La3-xTe4, p-type Yb14MnSb11, and n- and p-type filled skutterudites (SKD) for potential integration into advanced power generation devices. The zintl material Yb14MnSb11 is part of the hot side segment of the thermoelectric (TE) couple that also includes nickel as a hot side electrode. The long-term stability of these materials in juxtaposition to each other is critical to the success of these devices that need to operate for a long time (17 years). This talk will discuss device performance and microstructural analysis relevant to TE couple performance and longevity with a particular focus on interface between the materials constituting the couple. The experimental work is being supplemented and supported by thermodynamic modeling based on a CALPHAD approach.

9:20 AM  Cancelled
Thermal-to-electrical Energy Conversion Using Ferroelectric Materials: G.P. Zheng1; 1Hong Kong Polytechnic University
    With the increasing concerns on the environmental protection, global warming, and limited resources of fossil fuel, efficient use of energy and the generation of clean electricity are of great importance. Harvesting electrical energy from waste heat or thermal radiation is one of the most important steps in improving the energy efficiency and generating clean electricity. In the past decade ferroelectrics or pyroelectric materials used as energy conversion materials have attracted considerable attention and are found to be very promising in thermal-to-electrical energy conversion. In this work, ferroelectric multilayer structures, thin films and composites are investigated to implement such novel concept of solid-state energy conversion, which possesses high power density and thermal efficiency. The reverse effect of thermal-to-electrical energy conversion which is usually termed as electro-caloric cooling is also implemented in those ferroelectrics.

9:40 AM  
The Thermodynamic Investigation of the Effect of CO2áto the Stability of (La0.8Sr0.2)0.98MnO3▒δ: Shadi Darvish1; Yu Zhong1; 1Florida International University
    Thermodynamic predictions regarding the formation of secondary phases in atmosphere containing CO2 on the (La0.8Sr0.2)0.98MnO3▒δ (LSM-20) surface and at the LSM-20/8YSZ interface have been studied using the CALculation of Phase Diagram (CALPHAD) approach. The effects of temperature, O2 partial pressure, CO2 partial pressure and the cathode composition on formation of secondary phases have been investigated and correlated with the available experimental results found in the literature. Our study predicts that the SrCO3 has the possibility to form on the surface and at triple phase boundaries as a result of CO2 exposure to the system. In addition, it is indicated that the CO2 exposure does not change the electronic/ionic carriers’ concentration in perovskite phase. The observed electrical conductivity drop is predicted to occur due to the formation of secondary phases such as LaZr2O7, SrZrO3 or SrCO3, at the LSM-20/8YSZ interface, resulting in the blocking of the electron/ion transfer paths.

10:00 AM  
Weight Loss Mechanism of (La0.8Sr0.2)0.98MnO3▒δ during Thermal Cycles: Shadi Darvish1; Yu Zhong1; 1Florida International University
    A new weight loss Mechanism of (La0.8Sr0.2)0.98MnO3▒δ (LSM-20) using the La-Sr-Mn-O thermodynamic database is proposed with respect to the compound energy formalism (CEF) model, utilizing the CALculation of Phase Diagram (CALPHAD) approach. Quantitative Brouwer diagram for LSM-20 in air was plotted according to the defect chemistry analysis of perovskite phase and the charge disproportionation for temperature range of 600-1400░C. The SDT experiments on weight loss show the thermodynamic and kinetics effect during the thermal cycles. It was found that the Schottky defects dominate during the thermal cycles for LSM-20.

10:20 AM Break