Phase transitions in PbYb_1/2Nb_1/2O₃ with different degree of compositional ordering

Abstract

Recently we found out that compositional ordering degree s of Yb³⁺ and Nb⁵⁺ ions in PbYb_1/2Nb_1/2O₃ (PYN) ceramics can be varied by means of high-energy mechanical activation. In the present work dielectric and X-ray diffraction studies of the three obtained PYN ceramic samples with differing s values have been carried out in a wide temperature range. The highly disordered (s ≈ 0) sample appeared to be cubic in the 20–350 °C range and exhibited a diffused and frequency-dependent permittivity maximum at T_m ≈ 80 °C. Samples with s = 0.69 and 0.82 were orthorhombic at room temperature and exhibited non-diffused and frequency-independent permittivity maximum at T_m ≈ 170 and 250 °C respectively. However even in the most ordered PYN sample (s ≈ 0.82) cubic paraelectric and orthorhombic antiferroelectric phases coexist in the 190–300 °C temperature range.

Keywords:

• PbYb_1/2Nb_1/2O₃
• PYN
• phase transition
• compositional ordering
• mechanical activation

Additional information

Funding

This work was supported in part by the Ministry of Education and Science of the Russian Federation (research project No. 3.1649.2017/4.6) and by RFBR (projects 17-03-01293 and 17-02-00616).