Structural phase transitions coupled with prominent dielectric anomalies and dielectric relaxation in [(CH3)3NH]2[KCo(CN)6] and mixed [(CH3)3NH]2[KFexCo1−x(CN)6] double perovskite hybrids. Issue 6 (22nd January 2020)

• Record Type: Journal Article
• Authors: Rok, Magdalena; Zarychta, Bartosz; Moskwa, Marcin; Dziuk, Błażej; Medycki, Wojciech; Bator, Grażyna
• Is Part Of: Dalton transactions. Volume 49:Issue 6(2020)
• Page Start: 1830
• Page End: 1838
• Publication Date: 2020-01-22
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c9dt04703d
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : Structural phase transition and dielectric anomalies measured in pure and mixed crystals (TrMAFe x Co1− x ). Abstract : The crystals of pure [(CH3 )3 NH]2 [KFe(CN)6 ] (TrMAFe ) and [(CH3 )3 NH]2 [KCo(CN)6 ] (TrMACo ) as well as their mixed crystals (TrMAFe x Co1− x ), with different ratios of x = 0, 0.12, 0.18, 0.49, 0.56, 0.73, 0.81, 1.0, have been grown from aqueous solutions. The structure of TrMACo has been determined at 360 K to be cubic ( Fm 3̄ m ). In phase II (100 K), the TrMACo crystal is monoclinic ( C 2/ c ). The thermal stability of the pure and mixed crystals has been determined by using both DTA and TGA. Based on the DSC results, we have found a single phase transition (PT) for both pure and mixed crystals. The Fe(iii ) concentration was estimated by using the SEM technique. We have found a linear relationship between the PT temperature ( T c ) and the molar concentration of Fe(iii ). Based on the obtained results, a phase diagram has been constructed. The mechanism of the structural PT has been discussed based on the results of dielectric relaxation and 1 H NMR and X-ray spectroscopy measurements. The results confirmed that the PT mechanism of both pure and mixed crystals is related to the change in the dynamic state of the TrMA + cations. The dielectric activation energy changes linearly with the mole fraction ranking from 35 to 38 kJ mol −1, for the mixed crystals.