Abstract
The mixed compound NaH2(PO4)0.48(AsO4)0.52.H2O, which has been examined by Raman spectroscopy, XRD powder and dielectric, exhibits solid–solid phase transitions and one reversible solid–liquid phase transition. Besides, the investigation of dehydration behavior of sodium dihydrogenate phosphate-arsenate monohydrate was undertaken in a temperature range from 253 K to 333 K. The onset temperature of dehydration was determined from changes in ionic conductivity and X-ray powder on heating. It was confirmed by the Raman study not only in the disappearance of the vibrations assigned to the PO4, AsO4 but also in the appearance of the new vibrations attributed to the (PO3), which constitutes the P-O-P chain, giving a polymer with the formula: NaH2(P2O7)x(As2O7)(1-x). The important variation was observed in all studies at 313 K, which could correspond to the transformation of the NDAP compounds of a solid crystal into a liquid form.
Highlights
The mixed compound NaH2(PO4)0.48(AsO4)0.52.H2O [1], which is crystallized in the orthorhombic system with a space group of P212121 has revealed three reversible solid–solid phase transitions and one reversible solid– liquid phase transition below the decomposition point at Td = 391 K
From the studies of Raman, XRD powder and ac-conductivity, we can come to the conclusion that the NDAP compounds were transformed from a solid crystal, before 313 K, to an intermediate state described by a liquid crystal form at 313 K
The present study has shown that the transformation of the NDAP compounds of a solid crystalline form before
Summary
The mixed compound NaH2(PO4)0.48(AsO4)0.52.H2O (denoted by NDAP) [1], which is crystallized in the orthorhombic system with a space group of P212121 has revealed three reversible solid–solid phase transitions and one reversible solid– liquid phase transition below the decomposition point at Td = 391 K This material belongs to a group of compounds that have intermediate properties between those of a normal salt and an acid, and undergoes a transition from a paraelectric to a superprotonic phase at room temperature [2] This is an important discovery for the compounds derived from the KDP family (KH2PO4) of the general formula MH2XO4 (where M is a monovalent cation: K, Rb, Cs and X is P or As), whose use is possible in technological applications (fuel cells ...). It is important to study this transition which consists in the passage of a solid state to an intermediate state described by liquid crystals that are present just before the start of decomposition
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
