Schottky effect in the Pr3Te4Pr2Te3 system

Abstract

The heat capacity of RTez (R = Pr, La; z = 1.33, 1.37, 1.47, and 1.50) has been measured in a vacuum adiabatic calorimeter over the temperature range 5 to 273 °K. The heat capacity contribution due to the Schottky effect has been determined. The energy level set (ϵi) of the 3H4 state of the Pr3+ ion split by the crystal field with Th3P4 symmetry is calculated using the method of Stevens equivalent operators in the point charge model. For Pr3Te4 ϵi = 0,27.5, 88.2 (a doublet), 113.5, 331.7, 338.3 (a doublet), 345.5 is found. The dependence of the first split levels on composition is examined. From the investigation of the entropy due to the Schottky effect, the conclusion is made that no transition except the Schottky anomaly does exist in the Pr3Te4–Pr2Te3 system in the temperature range 5 to 273 °K.

Heat capacity and thermal conductivity of multiferroics Bi1-xPrxFeO3

“…In the case of doping with rare-earth elements, a three-level system can emerge due to a distortion of the lattice parameters caused by the polar displacements of bismuth and iron ions from the initial positions, and a change in the bond angle between oxygen octahedra FeO 6 [11]. In the general case, the expression for the Schottky heat capacity can be obtained by differentiation of the particle mean energy at the energy levels C p ¼(kT 2 ) À1 (hE i 2 i -hE i i 2 ) [12]. In the case of the three-level model (at arbitrary material mass), the Schottky heat capacity is given as…”

Теплоемкость и диэлектрические свойства мультиферроика Bi-=SUB=-0.8-=/SUB=-Ho-=SUB=-0.2-=/SUB=-FeO-=SUB=-3-=/SUB=-

“…В общем случае выражение для теплоемкости Шоттки можно получить, дифференцируя среднюю энергию частиц на энергетических уровнях: [12]. Для трехуровневой системы эта формула принимает вид [13]: FeO 3 , на зависимости ε ′ (T ), так же как и на зависимости C p (T ), наблюдается вторая аномалия (∼ 583 K).…”

Теплоемкость мультиферроиков Bi-=SUB=-1-x-=/SUB=-Pr-=SUB=-x-=/SUB=-FeO-=SUB=-3-=/SUB=-

“…В общем случае выражение для теплоемкости Шотт-ки можно получить, дифференцируя среднюю энер-гию частиц на энергетических уровнях C p = (kT 2 ) [11]. Выражение для теплоемкости Шоттки в случае трехуровневой модели (при произволь-ной массе вещества) имеет вид [12] …”