Structural and electrical studies of olivine LiNi1 − x(Co0.5Mn0.5) x PO4 (0 ≤ x ≤ 1) at high temperature
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A series of olivine-structured of LiNi1 − x(Co0.5Mn0.5) x PO4 (0 ≤ x ≤ 1) compositions have been synthesized by two-step conventional solid-state method at high temperature of 1000 °C followed by slow cooling or quenching. The XRD patterns of the obtained samples confirmed the formation of LiNi1 − x(Co0.5Mn0.5) x PO4 (0 ≤ x ≤ 1) phase with orthorhombic structure, Pmna space group. The lattice parameters determined by Rietveld refinements increase significantly as Co and Mn substitute for Ni. The SEM images show that the sample x = 0.8 started to partially melt while x = 1 has fully melted at temperature 1000 °C. The AC impedance spectroscopy measurements have revealed that the conductivity measured at 300 °C of all the slow-cooled samples can be enhanced by quenching. The quenched sample with x = 0.8 showed the largest increment of conductivities from 3.70 × 10−8 S cm−1 to 1.05 × 10−6 S cm−1 as a function of the cooling condition.
KeywordsX-ray diffraction (XRD) Rietveld refinement Olivine-structured Electrical conductivity
This study is financially supported by the Ministry of Higher Education Malaysia through the Fundamental Research Grant Scheme 2014 (FRGS Grant No.: FRGS/1/2014/TK06/UNIMAP/02/5).
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