Thermal and dielectric properties of ferroelectric lead germanate single crystals doped with chromium ions (Pb5Ge3O11:Cr3+)

• Published in: Phase transitions Vol. 91; no. 9-10; pp. 923 - 931
• Main Authors: Bachulska, U., Jankowska-Sumara, J., Majchrowski, A., Chrunik, M., Zasada, D., Soszyński, A.
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis 03-10-2018; Taylor & Francis Ltd
• Subjects: Chromium; Crystals; Curie temperature; Dielectric properties; Electrical properties; Ferroelectric lead germanate; Ferroelectric materials; Ferroelectricity; Phase transitions; Single crystals; specific heat; Trivalent chromium
• ISSN: 0141-1594; 1029-0338
• DOI: 10.1080/01411594.2018.1507032

Single crystals of Pb
5
Ge
3
O
11
(PGO), pure and doped with Cr
3+
ions, were grown by means of Czochralski and Kyropoulos method, respectively. Structural, microstructural, thermodynamic and dielectric properties were investigated in terms of Cr
3+
-doping. The temperature dependences of molar heat capacity in the range 120-700 K at constant pressure (c
p
) for PGO and PGO:Cr
3+
(0.2%) crystals were shown. Wide λ-shape anomalies correspond to the second-order phase transitions from ferroelectric to the paraelectric phase taking place at 453 K and 431 K for PGO and PGO:Cr
3+
(0.2%), respectively. The temperature dependences of c
p
for investigated crystals were approximated by the Einstein function and near the Curie temperature the c
p
reaches the classical Dulong-Petit limited value ∼475 J·mol
−1
·K
−1
. Temperature dependences of dielectric permittivity measured along and perpendicular to the ferroelectric axis in the temperature range 300-550 K are investigated. These studies revealed anisotropic behavior of PGO and PGO:Cr
3+
(0.2%) crystals.