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Diffused phase transition of polycrystalline (Ba0.80Sr0.20)TiO3

Kajtoch C., Bąk W., Gabryś M., Handke B., Starzyk F.

Archives of Materials Science and Engineering

2009

Vol. 39, nr 2

88-91

Purpose: The purpose of this work was to determinate the influence of the 20% Sr substitutions (in sublattice A) on changes of the character of phase transition (PT) in comparison with pure barium titanate BaTiO3 (BT). Design/methodology/approach: Polycrystalline samples of (Ba0.80Sr0.20)TiO3 (BS20T) were prepared by calcinations method at temperature 1620 K. X-ray measurements were executed from 10 deg to 120 deg with the 0.008 deg step. Images of the morphology of the samples were taken by means of electron microscope Philips SEM 525M at room temperature. Dielectric measurements were performed with application of Quatro Cryosystem 4.0 Agilent Precision LRC meter HP4824A equipped with WinDETA 5.62 software Novocontrol. Measurements were taken under cooling with 2 K/min speed. Measuring electric field frequency was from the range 20 Hz - 1 MHz. Findings: The difference between the value of temperature of structural transition (cubic-tetragonal) equal 310K and the temperature Tm (the temperature of maximum of real part electric permittivity) equal 340 K was affirmed. It was affirmed, that 20% substitution of Sr ions changed the type of phase transition. The transition was strongly diffused (DPT). The polar character of this solid solution was also observed in a broad temperature range (in the paraelectric phase too). It is connected with the occurrence of polar regions (clusters). Research limitations/implications: The results can be used to describe changes of PT in the DPT solid solutions with ferroactive substitutions in sublattice A. Originality/value: Value of this work relies on the experimental examination of the dielectric properties of (Ba0.80Sr0.20)TiO3 (BS20T) solid solution. The temperature of the DPT was calculated. The low value of phase angle is connected with the existence of the polar regions.