Crecimiento y medidas de las propiedades termicas en cristales Cs2ZnI4, {lcub}N(CH3)4{rcub} 2CoCl4, y Cs2CoCl4 (Spanish text)

In this thesis we studied the thermal properties, such as specific heat, thermal conductivity, and heat flow, as function of the temperature for crystals of the A2BX4 type, specifically: Cs2ZnI 4, {lcub}N(CH3)4{rcub}ZCoCl4, and Cs2CoCl 4. These crystals were grown by slow evaporation and fast evaporation methods and the properties were measured by the thermoelectric chamber method realized by the research group of Dr. Dorial Castellanos and the Differential Scanning Calorimeter DSC 2920. In this way we verified the effectivity of our technique in comparison with the results of other authors, other methods, and different instruments.; Graphs of specific heat, thermal conductivity and heat flow as function of the temperature were constructed. It was found that these crystals go through a series of phase transitions. For the crystal Cs2ZnI4 these transitions occurred in the range of temperatures between -10 and 0°C associated with a transition of structural type related to incommensurability and between 37 and 45°C associated to the Jahn-Teller effect. For the crystal {lcub}N(CH3)4{rcub}2CoCl4 these transitions occurred between -15 and 21°C for the structural type and between 28.3 and 33.5°C associated to the Jahn-Teller effect. For the crystal Cs2CoCl4 it was found that at temperatures between 52 and 56.4°C there is a non structural phase transition associated with the Jahn-Teller effect of which some features can be appreciated at temperatures as low as 18.9°C.