Synthesis of Aurivillius Phase CaBi4Ti4O15 Doped with both La3+ and Mn3+ Cations: Crystal Structure and Dielectric Properties

Abstract

The four-layer Aurivillius CaBi 4 Ti 4 O 15 with introducing of La 3+ on the A-site and Mn 3+ on the B-site with the formula Ca 1-x Bi 3+x LaTi 4-x Mn x O 15 (x = 0, 0.2, 0.4, 0.6, 0.8, and 1) were synthesized by molten salt method using the mixture of sulfate salts K 2 SO 4 /Na 2 SO 4 as the flux. XRD data confirmed the formation of single-phase Aurivillius with A2 1 am orthorhombic structure for x = 0, 0.2, 0.4, and 0.6, whereas for x = 0.8 and 1, the impurity phases were observed. SEM analysis shows the anisotropic plate-like grains, which are a typical grain of Aurivillius phases. The cell volume decreases with increasing x, indicating a presence of mixed valences of Mn 3+ and Mn 4+. The dielectric constants increased with x, strongly correlated with the higher distortion of the structure, since the 6s 2 lone pair electrons of Bi 3+ cation increase. The presence of Mn 3+ unpaired electrons results in the increase of dielectric loss as increasing x.

Investigation on structure, dielectric and magnetic properties of the four-layer Aurivillius phase Pb1-Bi3.5+Nd0.5Ti4-Mn O15 prepared via molten salt method

“…The significant decrease of c parameter in x ¼ 0.5 might be further raised by the formation of smaller Mn 4þ ions (0.54 Å) compared to Mn 3þ (0.645 Å). A similar trend was also observed in Ca 1-x Bi 3þx LaTi 4-x Mn x O 15 , whereas the formation of Mn 4þ caused a decrease in c lattice parameters and volume cell [14]. The existence of Mn 4þ ions could also be expected to give rise to the magnetic ordering, as discussed further below.…”

“…This result shows that the substitution of 12.5% molar ratio La 3þ for Bi 3þ and 12.5% molar ratio Mn 3þ for Ti 4þ can be simultaneously substituted in PbBi 4 Ti 4 O 15 structure when the Pb:Bi ratio is adjusted accordingly. It was previously reported that the single-phase products of the four-layer Aurivillius compounds were obtained for the Mn substitution up to 15% using the molten salt method [9,13,14]. It was inferred that the substitution of Mn 3þ for 15% could be possible.…”

“…Recently, we have reported on the synthesis of Ca-containing fourlayer Aurivillius compound (CaBi 4 Ti 4 O 15 ) with the simultaneous substitution of both Ln 3þ and Mn 3þ , which were obtained the single-phase products. Both series of compounds exhibited the greater structural distortion and dielectric properties with increasing x (Mn 3þ ) composition [13,14]. In this work, we explore the Pb-containing four-layer Aurivillius (PbBi 4 Ti 4 O 15 ) since the Pb 2þ ions with 6s 2 lone pair electrons are expected to induce a higher structural distortion, which will likely favor the higher ferroelectricity.…”

Structure-property relationships in the lanthanide-substituted PbBi2Nb2O9 Aurivillius phase synthesized by the molten salt method

“…Fig. 7 shows the temperature dependence of the dielectric constant and dielectric loss of pelletized samples measured in the range 50 kHz to 1 MHz, which best reflects the intrinsic polarizability [35]. The density of the pellets was determined as 7.73 g/cm 3 , 7.57 g/cm 3 , and 7.64 g/cm 3 for PBNO, PBNO-La, and PBNO-Nd respectively, which in each case is greater than 93% of the theoretical density and indicates that the molten salt method produces dense grains [21].…”

Structural transformation in Mn-substituted Sr2Bi2Ta2TiO12 Aurivillius phase synthesized by hydrothermal method: A comparative study and dielectric properties

“…The synthesis of the multiferroic Aurivillius phase is challenging since the different characters of d 0 and d n ions with the various ionic radii possibly destroy the structure when partial substitutions are performed [18]. A conventional solid-state method is the most popular method applied in the preparation of the Aurivillius phase.…”