Europium(II) titanate

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 T_N = 5.5 K, which has a significant influence on the dielectric constant.^[3][4][5]

Dried Eu₂O₃ and Ti₂O₃ are mixed 1:1 and reacted in an argon atmosphere at 1400 °C:^[3]

Eu₂O₃ + Ti₂O₃ → 2 EuTiO₃

The europium is reduced and the titanium is oxidized.

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]