Structural and electrical characterization of xBiScO3–(1−x)BaTiO3 thin films

Abstract

Using a tolerance factor approach, it was predicted that xBiScO3–(1−x)BaTiO3 will have a morphotropic phase boundary that should enhance both the polarizability and permittivity, relative to the BiScO3 end member, near a composition of x=0.4. To verify this prediction, pulsed laser deposition was used to grow xBiScO3–(1−x)BaTiO3 thin films on (100) SrRuO3∕LaAlO3 and Pt-coated Si substrates. Typical growth conditions were 700°C and 100mTorr O2∕O3. The perovskite structure was found to be stable for compositions of x=0.2–0.6 in epitaxial films, with reduced stability in polycrystalline films. The temperature where the maximum permittivity occurs rises as BiScO3 is added to BaTiO3, and increasingly relaxorlike behavior is observed with increasing BiScO3 content. Room temperature permittivity values ranged from 200 to 400, with loss tangents of ∼0.1 at 10kHz. The experimental morphotropic phase boundary occurs near x=0.4. 0.4BiScO3–0.6BaTiO3 showed a broad permittivity maximum near 800 from 150–275°C. Films with x=0.4 show a coercive field of about 200kV∕cm with a modest room temperature remanent polarization near 8μC∕cm2. The films exhibit a dielectric tunability of greater than 25% at fields of ∼500kV∕cm. The combination of high polarizability and high transition temperature makes this family an interesting base composition for lead-free piezoelectrics, especially if the degree of relaxor character could be reduced.

High temperature dielectric ceramics: a review of temperature-stable high-permittivity perovskites

“…A single, very diffuse relaxor r-T response occurred for compositions around x = 0.2BS: this gave rise to near-stable r values, 800-1000 over a wide temperature range [20]. Similar behaviour had previously been observed in thin film samples [21]. For x = 0.3 bulk ceramics, values of r ~ 1000 were recorded from temperatures of 0 to 300ºC, with high electrical resistivity, ~ 10 12 cm at 250ºC.…”

Phase transitions and ferroelectric properties in BiScO3-Bi(Zn1∕2Ti1∕2)O3-BaTiO3 solid solutions

“…Recently, Tinberg et al reported ferroelectric thin films based on the BiScO 3 -BaTiO 3 binary system. 12 Similar to the BiScO 3 -PbTiO 3 system, when PbTiO 3 was replaced with BaTiO 3 , the perovskite structure was stabilized and a MPB was observed. Although there are no reports related to the Bi͑Zn 1/2 Ti 1/2 ͒O 3 -BaTiO 3 system, an increased transition temperature can be expected for this system.…”

Simultaneous achievement of high dielectric constant and low temperature dependence of capacitance in (111)-oriented BaTiO3-Bi(Mg0.5Ti0.5)O3-BiFeO3 solid solution thin films

“…The low temperature dependence of the dielectric properties for the pseudocubic phase is in good agreement with previous reports for sintered bodies formed using BaTiO 3 -BiMO 3 solid solutions. [13][14][15][16][17][18][19] This is considered to be related to the relaxed behavior of these solid solutions, and the diffused temperature dependence of ε r , which reduces the overall temperature dependence of ε r . 20 In contrast, Mitsui et al reported that the maximum ε r was observed at more than 400 • C for x = 0.60.…”

“…11,12 Also, a low ε r temperature dependence has been reported for solid solution systems of BaTiO 3 and Bi-based perovskite oxides with pseudocubic structures at room temperature. Sintered bodies of BaTiO 3 -BiMO 3 [where M = Sc 3+ , Al 3+ , (Mg 0.5 Ti 0.5 ) 3+ , and (Zn 0.5 Ti 0.5 ) 3+ ] with pseudocubic symmetry show particularly high ε r stability at temperatures up to 400 • C. [13][14][15][16][17][18][19] In a previous study, we investigated the dielectric properties of ternary BaTiO 3 -Bi(Mg 0.5 Ti 0.5 )O 3 -BiFeO 3 solid solution films prepared by chemical solution deposition (CSD) as alternatives to BaTiO 3 -based high-ε r materials. 20 This system has a wide compositional region with a pseudocubic symmetry between the tetragonal and rhombohedral symmetries at room temperature.…”