Dielectric properties, thermal expansion and heat capacity of (1 − x)Na0.5Bi0.5TiO3-xBaTiO3 single crystals (x = 0, 0.02, 0.025, 0.0325 and 0.05)

High-quality and large-size lead-free (1 − x)Na0.5Bi0.5TiO3-xBaTiO3 single crystals (x = 0, 0.025, 0.0325 and 0.05) were grown using Czochralski method. The obtained samples were of pure perovskite structure with rhombohedral symmetry at room temperature. Thermal expansion, heat capacity, ferroelectric and dielectric properties were measured in a wide temperature range. The broad anomalies observed in thermal expansion and heat capacity were corresponded to structural, ferroelectric and dielectric anomalies, related to temperature features of polar regions and formation of a long-range order ferroelectric phase. The Burns temperature was found to increase with increasing BaTiO3 content. At low-frequency (100 Hz-100 kHz) the samples showed diffuse phase transitions. The obtained results were discussed in terms of local electric and strain fields caused by a difference in ionic radii between (Na,Bi) and Ba ions.