Synthesis and Li+ ion conductivity of Li2O–Nb2O5–P2O5 glasses and glass–ceramics

Abstract Glasses with the compositions of x Li 2 O–(70 − x )Nb 2 O 5 –30P 2 O 5 , x = 30–60, and their glass–ceramics are synthesized using a conventional melt-quenching method and heat treatments in an electric furnace, and Li + ion conductivities of glasses and glass–ceramics are examined to clarify whether the glasses and glass–ceramics prepared have a potential as Li + conductive electrolytes or not. The electrical conductivity ( σ ) of the glasses increases monotonously with increasing Li 2 O content, and the glass of 60Li 2 O–10Nb 2 O 5 –30P 2 O 5 shows the value of σ = 2.35 × 10 −6 S/cm at room temperature and the activation energy ( E a ) of 0.48 eV for Li + ion mobility in the temperature range of 25–200 °C. It is found that two kinds of the crystalline phases of Li 3 PO 4 and NbPO 5 are formed in the crystallization of the glasses and the crystallization results in the decrease in Li + ion conductivity in all samples, indicating that any high Li + ion conducting crystalline phases have not been formed in the present glasses. 60Li 2 O–10Nb 2 O 5 –30P 2 O 5 glass shows a bulk nanocrystallization (Li 3 PO 4 nanocrystals with a diameter of ∼70 nm) and the glass–ceramic obtained by a heat treatment at 544 °C for 3 h in air exhibits the values of σ = 1.23 × 10 −7 S/cm at room temperature and E a = 0.49 eV.