Heat capacity of (Cr 1− xNi x) 3Te 4 ( x=0–0.2) at high temperatures

Abstract

Heat capacities of (Cr 1− x Ni x ) 3Te 4 ( x=0–0.2) were measured from 325 to 920 K by using an adiabatic scanning calorimeter. Heat capacity anomalies due to the order–disorder of chromium atoms and vacancies were observed for all (Cr 1− x Ni x ) 3Te 4 ( x=0–0.1) samples around 800–900 K. The transition temperatures, transition enthalpy and entropy changes decreased with increasing doped nickel contents. The order–disorder transition mechanism will be discussed on the basis of entropy analysis. For (Cr 1− x Ni x ) 3Te 4 ( x=0.15 and 0.2) samples, another heat capacity anomaly in addition to the order–disorder transition mentioned above was observed around 600–700 K, probably due to the order–disorder transition in NiAs-type crystal structure. From X-ray and heat capacity results, the solubility limit of nickel to Cr 3Te 4 was determined to be around x=0.1.