SrTiO3 Content Research Articles

The variation of phase transition behavior on substituting Pb2+ and Sr2+ for a site cations in (Na1/2Bi1/2)TiO3 system

The phase transition behavior in (Na1/2Bi1/2)1-xPbxTiO3[NBPT(x)] and (Na1/2Bi1/2)1-xSrxTiO3[NBST(x)] with respect to changes in composition and temperature was investigated using X-ray analysis and dielectric characterization. Morphotropic phase boundary(MPB) are located in the composition range of 0.13 < × < 0.15 and 0.25 < × < 0.26 in NBPT(x) and NBST(x), respectively. The phase transition exhibited more 1st order behavior and the dielectric loss could be suppressed at high temperatures with the increase of Pb2+ substitutions. NBST(x) showed diffuse phase transition and the degree of the shift in permittivity peak with the measuring frequency increased with the increase of SrTiO3 content. This increase was correlated with the symmetry at room temperature and decrease of the temperature of maximum permittivity

Structural and electrical properties of rf magnetron-sputtered Ba1−xSrxTiO3 thin films on indium-tin-oxide-coated glass substrate

Structural and electrical properties of rf magnetron-sputtered Ba1−xSrxTiO3 thin films (x=0, 0.25, 0.5, 0.75, 1) on indium-tin-oxide-coated glass substrate were studied. The dense Ba1−xSrxTiO3 thin films sputtered from five different targets at the deposition temperature of 550 °C had individual orientations. The results of compositional analysis in films showed the deviation from the stoichiometry [(Ba+Sr)/Ti=1.009−1.089] with the increase of SrTiO3 content in the targets. The tetragonality in crystallographic structure of Ba1−xSrxTiO3 thin films was not observed even in the case of &amp;lt;x=0.3. The large frequency and composition dependence of ε′ and tan δ were also observed. There were no significant changes in ε′ up to x=0.5; however, the maximum value (ε′=204 at 100 kHz) around x=0.25 was in accordance with the results of bulk Ba1−xSrxTiO3 except at 1000 kHz. Above x=0.5, however, larger decreases of the dielectric constant were observed. The maximum values of ε′ in x=0.25, 0.5, 0.75 were shown around the measuring temperatures of 50, 25, −20 °C, respectively, indicating the diffuse phase transition in Ba1−xSrxTiO3 thin films. The observed increases in ε′ and tan δ above 125 °C are well explained with the barrier model. Nonlinear current-voltage characteristics in Ba1−xSrxTiO3 thin films showed that the lower the SrTiO3 content, the leakier Ba1−xSrxTiO3 thin films became, and the increase of SrTiO3 content leads to the increase of the breakdown fields from 1.7 to 2.7 MV/cm.

Preparation and properties of (Ba, Sr)TiO 3 single crystals

High quality solid solution single crystals of (Ba xSr1 -x)TiO 3 (BST) with any value of x can be pulled from a melt containing about 36 mol-% BaO/SrO and 64 mol-% TiO 2. The low frequency dielectric behaviour resembles that of the respective ceramics. The character of phase transition changes from 1st to 2nd order when the SrTiO 3-content exceeds around 50 mol-%. Accordingly the dielectric nonlinearity constant of the free crystal reverses its sign at that composition.