Analysis of thermal and electrical conductivity properties of Al substitution LiHf2(PO4)3 chemical solid electrolyte

Lithium ion conducting solid electrolytes, lithium aluminum hafnium phosphate (Li1+xHf2−xAlx(PO4)3, x = 0–0.75) are prepared via solid state synthesis technique. Thermo-gravimetric analysis indicates that the thermal decomposition and thermal stability of the reaction mixture is generally affected by a high content of x value substitution. It can be observed that as x content or aluminum substitution increases, the thermal decomposition and thermal stability increase which leads to the sample formation towards higher temperature. For X-ray diffraction analysis, the Rietveld refinement analysis indicates the presence of different types of secondary phases as aluminum content increases. Single phase of lithium hafnium phosphate (LiHf2(PO4)3) is only achievable in the absence of any aluminum substitution. Furthermore, for the lithium ionic conductivity, the findings indicate that conductivity increases with increase in x substitution in lithium aluminum hafnium phosphate. The highest AC conductivity is observable in the sample with composition x = 0.25 of about 2.5 × 10−3 Ω−1m−1 with low activation energy 0.36 eV. The present studies recommend the sample with composition x = 0.25 (Li1.25Hf1.75Al0.25(PO4)3) to be a future solid electrolyte material for battery applications.