Английская Википедия:Europium(II) titanate

Содержание

Текст

Текст

Текст

Текст

Текст

Текст

Текст

Текст

Текст

Europium(II) titanate is a black mixed oxide of europium and titanium, with the chemical formula of EuTiO₃. It crystallizes in the perovskite structure.

History

EuTiO₃ was first examined in 1966 by McGuire, Shafer, Joenk, Halperin and Pickart where the magnetic structure was examined. 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.

Preparation

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

<chem>Eu2O3 + Ti2O3 -> 2EuTiO3</chem>

The europium is reduced and the titanium is oxidized.

Properties

Шаблон:Technical Europium(II) titanate has two different crystal forms depending on the temperature. The phase transition occurs at 282 K. 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 PmШаблон:Overbarm (space group No. 221) with lattice parameter a = 390.82(2) pm (measured at 300 K). The transition temperature of the crystal structure from the low-temperature to the high-temperature phase increases with increasing pressure. The compound becomes G-type antiferromagnetic below 5.5 K. The specific heat capacity is 125 J·mol⁻¹·K⁻¹ (at 600 K). 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).