Ionic conductivity of Mn~(2+) doped dense tin pyrophosphate electrolytes synthesized by a new co-precipitation method

摘要

Mn~(2+) -doped Sn_(1-x)Mn_xP_2O_7 (X=0-0.2) are synthesized by a new co-precipitation method using tin(II)oxalate as tin(IV) precursor, which gives pure tin pyrophosphate at 300°C, as all the reaction by-products are vaporizable at <150°C. The dopant Mn~(2+) acts as a sintering aid and leads to dense Sn_(1-x)Mn_xP_2O_7 samples on sintering at 1100°C. Though conductivity of Sn_(1-x)Mn_xP_2O_7 samples in the ambient atmosphere is 10~(-9)-10~(-6) S cm~(-1) in 300-550°C range, it increases significantly in humidified (water vapor pressure, pH_2O = 0.12 atm) atmosphere and reaches >10~(-3)S cm~(-1) in 100-200 °C range. The maximum conductivity is shown by Sn_(0.88)Mn_(0.12)P_2O_7 with 9.79 × 10~(-6) S cm~(-1) at 550 °C in ambient air and 2.2 ) × 10~(-3) S cm~(-1) at 190 °C in humidified air. It is observed that the humidification of Sn_(1-x)Mn_xP_2O_7 samples is a slow process and its rale increases at higher temperature. The stability of Sn_(1-x)Mn_xP_2O_7 samples is analyzed.