Processing and Properties of Eu³⁺‐Doped Barium Bismuth Titanate (BaBi₄Ti₄O₁₅) Glass–Ceramic Nanocomposites

Abstract

Precursor glasses for the ferroelectric barium bismuth titanate (BaBi 4 Ti 4 O 15 ) (BBiT) have been prepared by the melt-quench technique in the SiO 2 -K 2 O-BaO-Bi 2 O 3 -TiO 2 (SKBBT) glass system with and without Eu 2 O 3 doping. BBiT glass-ceramic (GC) nanocomposites have been derived from these glasses by controlled heat treatment. The structural properties of the GCs have been investigated using X-ray diffraction (XRD), electron microscopy (FE-SEM, TEM), and FT-IR reflectance spectroscopy. FE-SEM images show the formation of randomly oriented hexagonal rod-shaped crystals of 200-400 nm and TEM images show 10-20 nm crystallites. FT-IR spectra exhibit the characteristic bands of BBiT at 480, 585, and 680 cm À1 . The activation energy of crystallization (E c ) varies from 295 to 307 kJ/mol. The dielectric constants (e r ) of glass and GC nanocomposites increase with an increase in frequency up to 3.0 MHz and then decrease up to 5.0 MHz. Heat-treated GCs show higher e r values, in the range 25-55, compared to the precursor glasses (20-37). Dielectric losses (tan d) for all the samples increase from 0.005 to 1.0 with an increase in frequency from 100 Hz to 5.0 MHz. Excitation spectra were recorded by monitoring emission at 613 nm corresponding to the 5 D 0 ? 7 F 2 transition. An intense 466 nm excitation band corresponding to the 7 F 0 ? 5 D 2 transition was observed. Emission spectra were then recorded by exciting the glass samples at 466 nm. Longer heat-treatment times led to a 15-fold increase in the intensity of the red emission at 612 nm, attributed to the segregation of Eu 3+ ions into the low phonon energy BBiT crystallites. The hardness (3.8-5.1 GPa) and fracture toughness (1.8-3.5 MPam 0.5 ) values obtained in the GCs are high and suitable for structural applications. II. Experimental ProcedureSix glasses with a molar composition of (100Àx) KS 2 -xBBiT (where KS 2 is K 2 OÁ2SiO 2 , x = 10, 20, 30, 40, 50, and 60 and BBiT corresponds to BaOÁ2Bi 2 O 3 Á4TiO 2 [BaBi 4 Ti 4 O 15 ]) were prepared from high-purity chemicals, namely SiO 2 (99.8%; Sipur A1 Bremtheler Quartzitwerk, Usingen, Germany), anhydrous potassium carbonate, K 2 CO 3 (GR, 99.9%; Loba Chemie, Mumbai, India), titanium (IV) oxide, TiO 2 (99.3%; J. Jones-contributing editor Manuscript No. 32359.

Structure, Ferroelectric and Photoluminescence Properties of Eu-Doped CaBi4Ti4O15 Multifunctional Ceramics

“…Three main emission bands located at 590 nm, 595 nm and 616 nm are assigned to the transitions of the 5 D 0 -7 F 0 , 5 D 0 -7 F 1 , and 5 D 0 -7 F 2 levels of Eu 3+ , respectively. The emission peak near 616 nm should be attributed to the electric dipole transition, suggesting that Eu 3+ occupies a non-centrosymmetric site in CaBi 4 Ti 4 O 15 host lattices, 26 which is consistent with the distortion of the lattice (Fig. 1).…”

Effect of topological structure on photoluminescence of PbSe quantum dot‐doped borosilicate glasses

“…The absorption band in 750‐650 cm −1 region is ascribed to the Al–O bending vibration of [AlO 4 ] unit, Si–O bending vibration of [SiO 4 ] tetrahedron unit, and the B–O bending vibration of planar [BO 3 ] unit . The absorption peak located at 1010 cm −1 might be contributed from the B–O asymmetric stretching vibration of [BO 4 ] tetrahedron unit and the Si–O stretching vibration of [SiO 4 ] tetrahedron unit . The weak absorption peak present at 1250 cm −1 is ascribed to asymmetric stretching vibration of B–O bond from ortho‐borate group .…”