Chemical compound
Europium(II) titanate is a black mixed oxide of europium and titanium, with the chemical formula of EuTiO3. It crystallizes in the perovskite structure.[1]
History
EuTiO3 was first examined in 1966 by McGuire, Shafer, Joenk, Halperin and Pickart where the magnetic structure was examined.[2] This compound received more attention at the beginning of the 21st century (2001 to 2015) due to the low-temperature phase transition to antiferromagnetic behavior at TN = 5.5 K, which has a significant influence on the dielectric constant.[3][4][5]
Preparation
Dried Eu2O3 and Ti2O3 are mixed 1:1 and reacted in an argon atmosphere at 1400 °C:[3]
The europium is reduced and the titanium is oxidized.
Properties
Europium(II) titanate has two different crystal forms depending on the temperature. The phase transition occurs at 282 K.[3][6] The low temperature form crystallizes in the tetragonal space group I4/mcm (space group No. 140) with the lattice parameters a = 551.92(2) pm, c = 781.64(8) pm (measured at 90 K). The higher temperature form has a cubic form with Pm3m (space group No. 221) with lattice parameter a = 390.82(2) pm (measured at 300 K).[3][7] The transition temperature of the crystal structure from the low-temperature to the high-temperature phase increases with increasing pressure.[8] The compound becomes G-type antiferromagnetic below 5.5 K.[9] The specific heat capacity is 125 J·mol−1·K−1 (at 600 K).[1] 125 J·mol−1·K−1290 K is 7,6 W·m−1·K−1 and the electrical conductivity is 105 (Ω·m)−1(at 330 K).[1]
