Shouhua Feng

Ionic conductivity in layered Na3Mo2P2O11(OH)·2H2O

Abstract Proton and sodium conductivities of Na 3 Mo 2 P 2 O 11 (OH)·2H 2 O have been studied from 25 to 460°C. The proton conductivity ranged from ∼6×10 −6 S/cm at 26°C to ∼2×10 −5 S/cm at 60°C ( E a =32kJ/mole and and log σ 0 =0.02 S/cm). The profile of proton conductivity as a function of relative humidity is similar to a type III Brunauer adsorption isotherm and suggests that the conduction mechanism is of particle hydrate-type. The proton conductivities at 100°C are ∼5×10 −7 S/cm for RH=6% and ∼9×10 −6 S/cm for RH=100%. Sodium ion conductivity was studied in the dehydrated phase with conductivities σ 267°C ∼2×10 −7 S cm ( E a = 104 kJ mole ) and σ 457° C ∼3×10 −3 S cm ( E a = 208 kJ mole ). The proposed conduction mechanism for sodium ion conductivity is similar to that in Na-β-alumina.

Proton Conducting Solid Electrolytes for High Temperature Humidity Sensing

The properties of various proton conducting solid electrolytes were investigated by electrochemical galvanic cell and ac impedance type measurements for applications as high temperature (T>200°C) humidity sensors. The basic characteristics of proton conductors required for humidity sensing are reviewed. Results of ionic conductivity and EMF measurements and their implications for the mechanism of ion transport are discussed for two prototype ceramic humidity sensors: β-Ca(PO 3 ) 2 and a NASICON-type ceramic composite, HZr 2 P 3 O 12 /ZrP 2 O 7 .