The dehydration behavior of the paraelectric phase of CsH 2PO4 was investigated by thermogravimetric and X-ray diffraction analyses, and then the phase diagrams of CsH2PO 4-CsPO3 system were established. The relationship between the onset temperature of dehydration (Tdehy/K) and the partial pressure of water (pH2O/atm) is log pH2O=7.62(±1. 18) -4.42(±0.56)(1000/Tdehy) below 228°C. The thermodynamically stable phase just above Tdehy is the fully dehydrated product CsPO3 (s), although partially dehydrated products transiently appeared in the course of the dehydration to CsPO3. Such developments allowed us to complete the temperature-humidity phase diagram and to regard the composition-temperature phase diagram as the eutectic type. This paper also reports the phase transition and electrical properties of CsPO3 examined by differential thermal analysis, ac impedance spectroscopy, and dc polarization measurement. The just-synthesized CsPO3 showed the relatively high electrical conductivity in unhumidified Ar. Ionic conductivity as high as 5× 10-4 S cm-1 was observed on heating from 150 to 450°C. Such high ionic conductivity disappeared after first heating up to 620°C and was explained by the proton diffusion through the absorbed H2O. At around 600°C, a high-temperature phase of CsPO3 showed the electrical conductivity as high as 10-3 S cm-1. However, this conductivity was not purely ionic.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Renewable Energy, Sustainability and the Environment
- Surfaces, Coatings and Films
- Materials Chemistry