Ruhiyuddin Mohd Zaki
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Preferred name
Ruhiyuddin Mohd Zaki
Official Name
Ruhiyuddin, Mohd Zaki
Alternative Name
Ruhiyuddin, M. Z.
Mohd Zaki, Ruhiyuddin
Zaki, Ruhiyuddin Mohd
Ruhiyuddin, Mohd Zaki
Zaki, R. Mohd
Mohd Zaki, R. S.R.
Zaki, R. M.
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Scopus Author ID
55560602300

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  • Publication
    The effect of Sn doping on the thermoelectric properties of SiGe using first principle technique
    (Trans Tech Publications Ltd., 2020)
    Abdullah Chik
    ;
    Haw Wei Kheng
    ;
    Ruhiyuddin Mohd Zaki
    ;
    Akeem Adekunle Adewale
    ;
    Faizul Che Pa
    ;
    Yeoh Cheow Keat
    The thermoelectric properties of hexagonal SiGe doped with Sn with doping percentage of 12.5% and 25% were investigated using linearised augmented plane wave method using the WIEN2k package and semiclassical Boltztmann Transport equation using the BoltzTraP software for the purpose of understanding the role of Sn as a dopant in the SiGe. For temperature range of 300 to 1000 K, it can be seen that by doping with Sn, there is an improvement in overall thermal conductivity of the samples with the highest improvement is in the 25% doped sample. The conductivity vs temperature for 25% Sn doped SiGe also shows higher value through temperature range from 300 K to 1000 K, however the Seebeck coefficient decreases with Sn doping percentage for the same temperature range. Due to lower Seebeck coefficient and higher thermal conductivity values, the overall thermoelectric coefficient, ZT, of the doped compound is lower than the SiGe values with highest ZT equal to 0.29 and 0.17 at 650 K for 12.5% and 25% respectively while the ZT of simulated SiGe at 650 K is 0.35. Thus 25% Sn doping actually reduce the ZT but enhanced the thermal and electrical conductivity of SiGe for temperature range of 300 to 1000 K.
  • Publication
    Thermoelectric properties of Sm doped CaMnO₃ using density functional theory method
    (Trans Tech Publications Ltd., 2020-09)
    Abdullah Chik
    ;
    Ruhiyuddin Mohd Zaki
    ;
    Akeem Adekunle Adewale
    ;
    Faizul Che Pa
    ;
    Yeoh Cheow Keat
    The electronic structure and thermoelectric properties of CaMnO₃ doped with 8% and 17% f block element Sm using first principles calculations and semi-classic Boltzmann theory were presented in this paper. The G-type AFM phase is most stable among five phases for CaMnO3, however, with 8% and 17% Sm doping, these compounds became nonmagnetic phases. CaMnO₃ calculated electronic band structure shows an indirect band gap of 0.523 eV, which is underestimated by the density functional theory (DFT) calculations but the band gap explains the semiconducting behavior. However, with 8% and 17% Sm doping, the electronic bandstructure of these compounds exhibit metallic behavior, with Sm 4f and Mn 3d electrons contributing to conduction band, increasing the magnitude of conductivity for doped compounds. All temperature dependence Seebeck coefficient plots show n-typed conduction for all compound with reduced magnitude of Seebeck coefficient for doped compounds. The temperature dependence thermal conductivity plot shows overall thermal conductivity is reduced in Sm doped compound. CaMnO₃ with 17% Sm doping exhibit much higher ZT of 0.32 at 800 K showing enhanced thermoelectric properties at high temperature and suitability or high temperature energy conversion devices.