Influence of NH4-Rb substitution on the phase transitions with different kinds of proton disorder in mixed [(NH4)1-xRbx]3H(SO4)2 crystals
Baranov, A. I.
Dolbinina, V. V.
Yakushkin, E. D.
Vinnichenko, Yu. V.
Schmidt, V. Hugo
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The role of ammonium ions in order–disorder ferroelastic, ferroelectric and structural phase transitions was studied in mixed [(NH4)1–x Rb x ]3H(SO4)2 0 < x < 1 crystals by dielectric spectroscopy and ac calorimetry. A new superprotonic phase was detected in compounds with x > 0·6. It was found that small Rb concentrations, x < 0·05, strongly smear out the temperature anomalies of dielectric constant and specific heat for phase transitions II–III, III–IV, IV–V and V–VIII. At x > 0·09 these phase transitions are fully suppressed. Finally, for Rb concentrations 0·05 < x < 0·9 a proton glass phase appears below 35 K.
A.I. Baranov, V.V. Dolbinina, E.D. Yakushkin, V.Yu. Vinnichenko, V.H. Schmidt, and S. Lanceros‑Mendez, “Influence of NH4-Rb substitution on the phase transitions with different kinds of proton disorder in mixed [(NH4)1-xRbx]3H(SO4)2 crystals,” Ferroelectrics 217, 285-295 (1998).