Effect of Tin Addition on the Phase Transitions of Ferroelectric Barium Titanate from Tetragonal to Cubic Crystal System

Abstract

Solid solutions of tin-doped barium titanate (BaTi_1-xSn_xO₃) were synthesized by solid-state reaction method at calcining temperature 1200˚C and time 2h for ratios x=0, 0.05, 0.07, 0.1, 0.12, 0.15, 0.17. The structural properties of the prepared samples were studied using X-ray diffraction technique (XRD). The diffraction patterns confirmed the formation of the pure and tin-doped barium titanate phase. The experimental results also showed that compounds with ratios x = 0, 0.05, 0.07 possessed the tetragonal crystal system, and it was found that both the tetragonal and cubic crystal systems were formed in the ratio x=0.1, while the samples with proportions x = 0.12, 0.15, 0.17 had the cubic crystal system. The intensity of dislocations was increased by tin doping due to the replacement of tin ions Sn⁴⁺ (r_i=0.83Å) by titanium ions Ti⁴⁺ (r_i=0.745Å) in the crystal lattice. The density of dislocations was highest in the sample with the ratio x = 0.1 because it contains two crystal systems tetragonal and cubic. The higher percentage of doping with tin causes an increase in the unit cell volume, and the crystallization rate in the samples decreased from 97% to 90%.