Tailoring the physicochemical and electrochemical properties of Mg0.5+x(Zr1-xAlx)2(PO4)3 ceramic electrolytes

In this study, samples of Nasicon-type structured Mg 0.5+ x (Zr 1- x Al x ) 2 (PO 4 ) 3 , (0.0 ≤ x ≤ 0.4) compound were synthesized via citrate assisted sol-gel method. The influences of structural modifications by partial substitution using trivalent ions (Al 3+ ) into the pristine Mg 0.5 Zr 2 (PO 4 ) 3 to the structural, particle size and electrical properties of the compounds were investigated. The crystal structure formation of Mg 0.5+ x (Zr 1- x Al x ) 2 (PO 4 ) 3 were affirmed using X-ray diffraction, while Rietveld refinement method was applied to clearly prove the formation of the structure. FESEM and particle size analysis confirmed that the particle size decreased with the increase of Al 3+ compositions. The substitutions of Zr 4+ with Al 3+ in the pristine compound structure introduced extra-interstitial Mg 2+ ions leading to enhanced conductivity. Mg 0.5+ x (Zr 1- x Al x ) 2 (PO 4 ) 3 compound with x = 0.4 exhibited the uttermost conductivity value of 7.33 × 10 −5 S cm −1 at 773 K with the lowest activation energy of ∼0.82 eV.