Abstract Li 2O–B 2O 3–P 2O 5 glass soot was fabricated from aqueous precursor solution of a CH 3CO 2Li·2H 2O and BCl 3, POCl 3 by the flame-assisted ultrasonic spray hydrolysis. The aqueous precursor solution of the lithium acetates was first atomized with an ultrasonic vibrator (1.7 MHz). B 2O 3 and P 2O 5 were formed from BCl 3 and POCl 3 by oxy-hydrogen flame. Their properties were investigated by SEM, XRD, TGA–DSC and impedance analyzer. The formed particles in glass soot had spherical shape and the size of approximately 50–100 nm. XRD analysis revealed that the amorphous phase and crystalline phases were mixed in glass soot and the crystalline phases were B(OH) 3 and B 2O 3. The crystalline B(OH) 3 and B 2O 3 found in glass soot completely disappeared by heat treatment. Conductivity was measured by complex impedance method using impedance analyzer and the conductivity was 10 −8 S/cm.