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Thermal analysis confirmed the presence of the phase transition at T = 320 K in the Cs2SeO4·H6TeO6 (CsSeTe) material. The structural study carried out at T = 360 K shows that this compound passes from the monoclinic system with the space group P 2 1 / c at room temperature, to the trigonal system with the space group R 3 ¯ m . At room temperature, the anionic groups are well ordered and stable, whereas after the transition at T = 320 K, the selenate groups change their orientation and the tellurate polyhedra change their positions. The high-temperature vibrational studies, carried out in a temperature range of 289–353 K, confirm the presence and nature of the transition detected by thermal analysis. The conductivity evolution versus temperature shows the presence of an ionic–protonic conduction phase transition at T = 490 K. [ABSTRACT FROM AUTHOR]

In the current research work, we investigated the growth of the new potassium arsenate tellurate material formulated as K2(HAsO4).Te(OH)6 (KAsTe) through the use of the slow preparation method. The (KAsTe) compound crystallized in the monoclinic system with centrosymmetric space group P21/c. Within this structure, two types of polyhedra (Te-O6 and HAsO4) were observed in the presence of K+ cations. The stability and the cohesion of the crystal structure were ensured by the linkage of different polyhedra via O‒H...O hydrogen bonds. To locate the closest contacts within this crystal structure, Hirshfeld surface analysis was performed. In fact, according to the fingerprint plots, we inferred that the hydrogen bonds constitute the dominant interactions present within this structure. The vibrational spectroscopy study at room temperature unveiled the occurrence and the independence of the ionic groups and provided detailed data on hydrogen bonds present in the crystal lattice. Thermal analyses (DSC, DTA, TG and MS) proved the presence of three phase transitions at 445, 514 and 555 K and indicated that no mass loss was recorded before 460 K. Furthermore, the σdc variation performed on (KAsTe) material suggested an important level of conductivity at high temperature, associated with the motion of H+ proton. This behavior goes in good agreement with the presence of the super‒ionic protonic phase transition at 445 K. [ABSTRACT FROM AUTHOR]

Simulated Nyquist plots with equivalent circuit elements for the (CsAsTe) compound at different temperatures. • Three phase transitions before the decomposition detected by Thermal study. • The variation of Raman spectra at high temperatures describes all phase transitions. • The conductivity evolution confirms that this material is an ionic– protonic conductor. The cesium hydrogeno–arsenate tellurate material (CsAsTe) was grown at room temperature by slow evaporation of aqueous solution, in order to determine the nature of all phases transitions as well as to specify the dielectric properties and electrical conduction mechanisms. The DTA, TG and the mass spectrometry analyses revealed that no mass loss was recorded before 425 K. The DSC thermogram demonstrates the presence of three phase transitions at 365 K, 379 K and 400 K. Raman spectra were performed at various temperatures so as to characterize the phase transitions. The dielectric and electrical properties were specified. In this process, the Nyquist plots (–Z″ versus Zʹ) were well fitted to an equivalent circuit built up by a series combination of grain and grain boundary elements. Furthermore, the DC conductivity evolution unveils the presence of the ionic–protonic conduction phase transition. The AC electrical investigation discloses that the conduction is insured by the correlated barrier hopping (CBH) model. The variation of M″ versus frequency proves that the conduction mechanism is thermally activated. [ABSTRACT FROM AUTHOR]

Representation of tunnels and hydrogen bonds in (KAsTe) structure. [Display omitted] • The effect of hydrothermal preparation method leads to a significant change affecting the polyhedra arrangement in (KAsTe) material. • Intermolecular interactions that are analyzed by Hirshfeld surfaces reveal the dominant interactions in (KAsTe) compound. • The DSC thermogram of this material demonstrates the presence of three phase transitions. • The conductivity evolutions prove that this compound is ionic-protonic conductors at high temperature. In the current research work, we investigated the growth of the new potassium arsenate tellurate material formulated as K 3 (HAsO 4)(H 2 AsO 4).Te(OH) 6 (KAsTe) through the use of the hydrothermal preparation method. The KAsTe compound was crystallized in the monoclinic system with centrosymmetric space group C 2/ c. Within this structure, two types of polyhedra (TeO 6 and HAsO 4) were observed in the presence of K+cations. The stability and the cohesion of the crystal structure were ensured by the linkage of different polyhedra via O-H∙∙∙O hydrogen bonds. To locate the closest contacts within this crystal structure, Hirshfeld surface analysis was performed. In fact, according to the fingerprint plots, we inferred that the hydrogen bonds constitute the dominant interactions present within this structure. The vibrational spectroscopy study at room temperature unveiled the occurrence and the independence of the ionic groups and provided detailed data on hydrogen bonds present in the crystal lattice. Thermal analyses (DSC, DTA, TG and MS) proved the presence of three phase transitions at 428, 510 and 553 K and indicated that no mass loss was recorded before 460 K. Furthermore, the σ dc variation performed on KAsTe material suggested an important level of conductivity at high temperature, associated with the motion of H+ proton. This behavior goes in good agreement with the presence of the super-ionic protonic phase transition at 428 K. [ABSTRACT FROM AUTHOR]