Dielectric properties of polycrystalline (Ba0.60Sr).40)Ti0.8O3

Purpose: The purpose of the work was to determinate the influence of the ferroactive Sr substitutions in sublattice A and the nonstoichiometry in sublattice B on changes of physical properties and the character of phase transition (PT) in pure barium titanate BaTiO3 (BT). Design/methodology/approach: The polycrystalline samples of (Ba0.60Sr0.40)TiO3 and (Ba0.60Sr0.40)Ti0.8O3 were obtained by the calcinations method in temperature 1620 K. The dielectric measurements were executed by automatic device (QUATRO KRIO 4.0 with LCR Agilent 4824A meter and BDS 1100 cryostat). The materials were investigated under cooling conditions with speed of 2 K/min and within frequency range from 20 Hz to 1 MHz. Findings: The dielectrometry was applied to measure complex dielectric permittivity and other dielectric functions of ferroelectric (Ba0.60Sr0.40)TiO3 (BST-40) and (Ba0.60Sr0.40)Ti0.8O3 (BST-40/0.8). It was affirmed, that 40% substitution of Sr ions as well as 20% deficiency of Ti ions in solid solution reduced temperature and changed the type of phase transformation. The transformation stood strongly diffused. The weak dependence of temperature Tm (peak of electric permittivity ε') from frequency of electric measuring field was observed. It means, that this material should be prescribed to the class of ferroelectrics with diffused phase transformation (DPT). The polar character of this solution was also observed in the paraelectric phase. It is connected with the occurrence of polar clusters in paraelectric phase. Practical implications: Results can be used to construct the model describing changes in the solid solutions with ferroactive and nonferroactive substitutions in sublattice A or B of the perovskite. Originality/value: Value of this work relies on the experimental examination of the electric properties of nonstoichiometric BST-40 solid solution. The low value of phase angle in the paraelectric phase was connected with the occurrence of the polar regions.