• Article  

      Effect of antimony-doping and germanium on the highly efficient thermoelectric Si-rich-Mg2(Si,Sn,Ge) materials 

      Vlachos, N.; Polymeris, G. S.; Manoli, M.; Hatzikraniotis, E.; Khan, A. U.; Lioutas, C. B.; Stefanaki, E. C.; Pavlidou, E.; Paraskevopoulos, K. M.; Giapintzakis, John; Kyratsi, Theodora (2017)
      Two series of materials (a) Mg2Si0.55-ySn0.4Ge0.05Sby, 0 ≤ y ≤ 0.0175 and (b) Mg2Si0.5875-xSn0.4GexSb0.0125, 0 ≤ x ≤ 0.20 have been developed and studied in terms of structural features and thermoelectric properties/performance. ...
    • Article  

      Effect of Bi-doping and Mg-excess on the thermoelectric properties of Mg2Si materials 

      Ioannou, M.; Polymeris, G. S.; Hatzikraniotis, E.; Paraskevopoulos, K. M.; Kyratsi, Theodora (2014)
      In this work, Bi-doped magnesium silicide compounds were prepared by applying a combination of both, short-time ball milling and heating treatment. The effect of Mg excess was also studied, aiming towards further improvement ...
    • Article  

      Effect of microstructure on the thermoelectric performance of La1−xSrxCoO3 

      Viskadourakis, Z.; Athanasopoulos, G. I.; Kasotakis, E.; Giapintzakis, John (2016)
      We present a case where the microstructure has a profound effect on the thermoelectric properties of oxide compounds. Specifically, we have investigated the effect of different sintering treatments on La1−xSrxCoO3 samples ...
    • Article  

      Effect of sintering in ball-milled K 2Bi 8Se 13 thermoelectric nano-composites 

      Hatzikraniotis, E.; Ioannou, M.; Chrissafis, K.; Chung, D. Y.; Paraskevopoulos, K. M.; Kyratsi, Theodora (2012)
      K 2Bi 8Se 13 has many attractive features for thermoelectric applications. Recently, K 2Bi 8Se 13-based nanocomposite materials, consisting of nano-crystalline, micro-crystalline and amorphous phases, have been fabricated ...
    • Article  

      High thermoelectric figure of merit of Mg2Si 0.55Sn0.4Ge0.05 materials doped with Bi and Sb 

      Khan, A. U.; Vlachos, N.; Kyratsi, Theodora (2013)
      Thermoelectric properties of new Bi- and Sb-doped Mg2Si 0.55Sn0.4Ge0.05 compounds prepared by powder methods were studied in the temperature range 300-823 K. The materials exhibited compositional inhomogeneites consisting ...
    • Article  

      Highly anisotropic crystal growth and thermoelectric properties of K 2Bi 8-xSb xSe 13 solid solutions: Band gap anomaly at low x 

      Kyratsi, Theodora; Dyck, J. S.; Chen, W.; Chung, D. Y.; Uher, C.; Paraskevopoulos, K. M.; Kanatzidis, M. G. (2002)
      The thermoelectric properties of solid solutions of the type β-K 2Bi 8-xSb xSe 13 (0<x<8) were studied with respect to thermal behavior, band gap variation, and charge transport properties as a function of x. At x values ...
    • Article  

      Modification of thermoelectric properties using insertion techniques 

      Hatzikraniotis, E.; Kyratsi, Theodora; Chrissafis, K.; Paraskevopoulos, K. M. (1999)
      In this work is presented the application insertion techniques for the modification of the performance of thermoelectric materials. The results indicate that in cases as in Bi2Se3 compounds where insertion of foreign species ...
    • Article  

      Solid-state synthesis and thermoelectric properties of Sb-doped Mg 2Si materials 

      Ioannou, M.; Polymeris, G.; Hatzikraniotis, E.; Khan, A. U.; Paraskevopoulos, K. M.; Kyratsi, Theodora (2013)
      Sb-doped magnesium silicide compounds have been prepared through ball milling and solid-state reaction. Materials produced were near-stoichiometric. The structural modifications have been studied with powder x-ray diffraction. ...
    • Article  

      Solid-state synthesis of Mg 2Si via short-duration ball-milling and low-temperature annealing 

      Ioannou, M.; Chrissafis, K.; Pavlidou, E.; Gascoin, F.; Kyratsi, Theodora (2013)
      In this work, a short duration ball-milling of elemental Mg and Si followed by a thermal treatment is suggested in order to synthesize magnesium silicide via solid-state reaction. The formation of magnesium silicide was ...
    • Article  

      Structural Characterization and Thermoelectric Properties of Hot-Pressed CoSi Nanocomposites 

      Ioannou, M.; Symeou, E.; Giapintzakis, John; Kyratsi, Theodora (2014)
      Fabrication of nanocomposites by introduction of SiO2 metal oxide nanoparticles into a cobalt silicide thermoelectric matrix is studied. The CoSi matrix material was prepared through solid-state synthesis, and the nano-SiO2 ...
    • Article  

      Structural features of ball-milled nanostructured K2Bi 8Se13 thermoelectric material 

      Lioutas, C. B.; Hatzikraniotis, E.; Ioannou, M.; Paraskevopoulos, K. M.; Kyratsi, Theodora (2011)
      In this work, K2Bi8Se13 material was ball-milled in order to develop nanostructures through the modification of structural features. Structural changes during ball-milling were followed by powder X-ray diffraction measurements, ...
    • Article  

      Synthesis, Crystallographic Studies, and Characterization of K 2Bi8Se13-xSx Solid Solutions 

      Kyratsi, Theodora; Kanatzidis, M. G. (2003)
      The detailed crystal structures of selected members of solid solutions of the thermoelectric compounds K2Bi8Se13-xS x with x = 4, x = 6 and x = 10 were determined. The purpose of this study was to understand the nature of ...
    • Article  

      Synthetic conditions and their doping effect on β-K2Bi8Se13 

      Kyratsi, Theodora; Kika, I.; Hatzikraniotis, E.; Paraskevopoulos, K. M.; Chrissafis, K.; Kanatzidis, M. G. (2009)
      In this work the synthetic conditions for K2Bi8Se13 and their effect on its thermoelectric properties were investigated. K2Bi8Se13 was prepared as a single phase using K2Se and Bi2Se3 as starting materials in a furnace or ...
    • Article  

      Thermoelectric properties of Bi0.5Sb1.5Te3 thin films grown by pulsed laser deposition 

      Symeou, E.; Pervolaraki, M.; Mihailescu, C. N.; Athanasopoulos, G. I.; Papageorgiou, C.; Kyratsi, Theodora; Giapintzakis, John (2015)
      We report on the pulsed laser deposition of p-type Bi0.5Sb1.5Te3 thin films onto fused silica substrates by ablation of dense targets of Bi0.5Sb1.5Te3 with an excess of 1 wt% Te. We investigated the effect of film thickness, ...
    • Article  

      Thermoelectric properties of hot-pressed β-K2Bi 8Se13-x Sx materials 

      Kyratsi, Theodora; Ioannou, M. (2013)
      In this work, hot-pressed pellets of the K2Bi8Se 13 family of compounds were prepared for the first time. The pellet fabrication of selected members of the K2Bi8Se 13-x Sx series was studied. Sintering parameters, such as ...
    • Conference Object  

      Thermoelectric properties of K 2Bi 8Se 13-xS x solid solutions 

      Kyratsi, Theodora; Lal, S.; Hogan, T.; Kanatzidis, M. G. (Affiliation: Department of Chemistry, Michigan State University, East Lansing, MI 48824, United StatesAffiliation: Department of Mechanical and Manufacturing Engineering, School of Engineering, University of Cyprus, Nicosia, CyprusAffiliation: Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI 48824, United StatesCorrespondence Address: Kyratsi, T.Department of Chemistry, Michigan State University, East Lansing, MI 48824, United States, 2006)
      Derivatives of β-K 2Bi 8Se 13 are an interesting series of materials for thermoelectric investigations due to their very low thermal conductivity and highly anisotropic electrical properties. Up to now substitutions on the ...
    • Article  

      Thermoelectric properties of nanocrystalline PbTe synthesized by mechanical alloying 

      Papageorgiou, Ch; Hatzikraniotis, E.; Lioutas, Ch B.; Frangis, N.; Valassiades, O.; Paraskevopoulos, K. M.; Kyratsi, Theodora (2010)
      In this work, nanocrystalline lead telluride powder was synthesized from high-purity elements by mechanical alloying by means of a planetary ball-milling procedure. The milling medium was tungsten carbide, and the diameter ...