Tuning the optical, electrical and magnetic properties of Ba_0.5Sr_0.5Ti_xM_1−xO₃ (BST) nanopowders

Abstract

Metal doped barium strontium titanate (BST; Ba0.5Sr0.5TixM1-xO3) nanopowders have been successfully synthesized through the oxalate precursor route based on low cost starting materials. The effect of metal ion substitution, namely Fe(3+), Mn(2+), Co(2+) and Y(3+), on the crystal structure, microstructure and optical, electrical, dielectric and magnetic properties of BST was studied. The results revealed that a crystalline single cubic BST phase was formed for pure and Mn(2+), Co(2+) and Y(3+) ion-substituted BST samples, whereas a tetragonal BST structure was obtained for the Fe(3+) substituted BST sample at an annealing temperature of 1000 °C for 2 h. Furthermore, addition of the metal ions was found to decrease the crystallite size and unit cell volume of the produced BST phase. The microstructure of the produced pure BST phase was metal ion dependent. Most BST particles appeared as a cubic like structure. The transparency of BST was found to increase with metal substitution. Meanwhile, the band gap energy was increased from 3.4 eV for pure BST to 3.8, 4.1, 4.2 and 4.3 eV as the result of substitution by Fe(3+), Mn(2+) and Co(2+) and Y(3+) ions, respectively. The DC resistivity was metal ion dependent. The highest DC resistivity (ρ = 66.60 × 10(5) Ω cm) was accomplished with the Mn(2+) ion. Moreover, the addition of metal ions decreased the dielectric properties of the expected Mn(2+) ion and increased the magnetic properties.

Magnetic and spectroscopic properties of Ni–Zn–Al ferrite spinel: from the nanoscale to microscale

“…The optical band gap (E g ) is the most important feature of materials that are good candidates for optoelectronic applications. The optical band gap (E g ) of the present Ni 0.6 Zn 0.4 Fe 1.5 Al 0.5 O 4 nanoparticles can be calculated experimentally from the optical absorption edge using the Tauc's relation as follows: 12,58 ahn…”

“…Knowledge of n is essential in the design of hetero-structure lasers in optoelectronic devices as well as in solar cell applications. 64 The refractive index (n 0 ) of ferrite nanostructures can be calculated from the value of E g using Moss empirical relation: 58,59 E g n 0 4 ¼ 104 eV…”

Enhancement of rotational vacuum friction by surface photon tunneling

“…As a ferroelectric material, BST possesses many exceptional dielectric properties such as high dielectric constant, low loss and large electric-field dielectric tunability over a wide frequency range [24]. Especially, it has low surface polariton frequency which is favorable for enhancing the vacuum friction torque at sub-GHz and GHz frequencies.…”

“…To measure the vacuum friction between a silica sphere and a silica plate, the experiment needs to be conducted under ultrahigh vacuum below 10 −9 torr [19]. In this work, we propose to use BST, which is a perovskite ferroelectric ceramic that can have a large dielectric resonance at GHz frequency [24], to dramatically enhance the vacuum friction by resonant surface photon tunneling at sub-GHz and GHz frequencies. We show that the vacuum frictional torque on a BST sphere near a BST plate can be significantly enhanced to 3.6 × 10 −24 Nm and 8.1 × 10 −23 Nm through resonant photon tunneling at a rotating frequency of 150 MHz and 3.5 GHz, respectively.…”

“…Such a high surface polariton frequency makes it extremely difficult to experimentally reach the resonant condition [25][26][27]. Here we choose a ferroelectric material BST which has low surface polariton frequency at GHz range [24]. The dielectric properties of BST can also be tuned by fabrication and doping.…”