In this study, the electrochemical properties of garnet-structured all-solid-state battery electrolytes (Li6.4La3Zr1.4Ta0.6O12,hereafter LLZTO) were assessed by altering the calcination temperature, while maintaining a consistent sintering duration. Among thevarious heat treatment conditions employed for sample fabrication, the ‘700_1100’ condition, denoting a calcination temperature of700°C and a sintering temperature of 1100°C, resulted in the most exceptional ionic conductivity of 4.89 × 10-4 S/cm and a relativedensity of 88.72% for the LLZTO material. This is attributed to the low calcination temperature of 700°C, leading to reduced grainsize and enhanced cohesiveness, thus resulting in a higher sintered density. In addition, a microstructure similar to the typical sinteringcharacteristics observed in Spark Plasma Sintering (SPS) methods was identified in the SEM analysis results under the ‘700_1100’condition. Consequently, the ‘700_1100’ heat treatment condition was deemed to optimal choice for enhancing ionic conductivity.