Crecimiento y medida de la constante dielectrica en cristales de rubidium-manganese-bromine, rubidium-cobalt-bromine y cesium-zinc-chloride

The dielectric constant of crystals of Rb₂CoBr₄, Rb₂MnBr₄, and Cs₂ZnCl₄ (dopped with CoCl₂), which were grown by slow evaporation technique, was measured using LCZ method in a temperature range of 271 to 355 K and a frequency interval of 10 Hz to 1 MHz. The behavior of the dielectric constant for each one of the compounds was analyzed varying the resonant frequency in the circuit. Later, the behavior of the dielectric constant was analyzed with temperature variations for certain specific values of frequency where the system showed greater susceptibility to changes and anomalies.; From the graphs of dielectric constant versus temperature, was possible to observe how the crystals experience a phase transition of structural type of the incommesurate phase to the normal phase for certain critical values of temperature. For Cs₂ZnCl₄ (dopped with CoCl ₂) the critical temperature at which this transition occurs is 322 K, for Rb₂CoBr₄ is 335 K and for Rb₂MnBr ₄ is 341 K. In the same way, the compounds present a phase transition of nonstructural type associated with the Jahn Teller effect for the following critical temperatures: 325 K for Cs₂ZnCl₄ (dopped), 351 K for Rb₂CoBr₄ and 343 K for Rb₂MnBr ₄. The appearance of this phase is compatible with results obtained in other compounds previously studied. It is possible that this phenomenon is common for many crystals belonging to family A₂BX₄.