Preparation of BaTi₄O₉ from Oxalates

Abstract

A barium titanate precursor with a barium:titanium ratio of 1:4 was prepared by controlled coprecipitation of mixed barium and titanium species with an ammonium oxalate aqueous solution at pH 7. The results of thermal analysis and IR measurement show that the obtained precursor is a mixture of BaC 2 O 4 ⅐0.5H 2 O and TiO(OH) 2 ⅐1.5H 2 O in a molar ratio of 1:4. Crystallized BaTi 4 O 9 was obtained by the thermal decomposition of a precipitate precursor at 1300°C for 2 h in air. The dimensions of the powder calcined at 1000°C are between 100 and 300 nm. The grain dimensions of the sintered sample for 2 h at 1300°C are of the order of 10 to 30 m. Dielectric properties of disk-shaped sintered specimens in the microwave frequency region were measured using the TE 011 mode. Excellent microwave characteristics for BaTi 4 O 9 -‫؍‬ 38 ؎ 0.5, Q ‫؍‬ 3800 -4000 at 6 -7 GHz and f ‫؍‬ 11 ؎ 0.7 ppm/°C-were found.

Microwave Dielectric Properties of Sol-Gel Derived BaTi4O9 and Ba2Ti9O20:B2O3 Ceramics

“…BaTi 4 O 9 ceramic was sintered at 1250 • C for 2 h, it has good properties (the resonant frequency f, ε r , Q factor and Q × f factor were 5.31 GHz, 36.1, 3220, and 17100 GHz, respectively). The ε r value is comparable with that of BaTi 4 O 9 ceramics from an oxalates route (38 ± 0.5) [13]. A ε value of 34.2 has been reported for Sn-doped BaTi 4 O 9 ceramics prepared by a citrate route [14].…”

Synthesis and Characterization of Low Loss Dielectric Ceramics Prepared from Composite of Titanate Nanosheets with Barium Ions

“…Phase composition of measured sample (calculated from XRD, data gathered in Table 1) is another factor influencing dielectric permittivity. In the case of BaTi 4 O 9 and Ba 2 Ti 9 O 20 , the maximum literature values of were equal to 39 [5] and 52 [28], respectively. The Ba-TN subjected to step sintering in a range of temperatures from 900 ∘ C to 1300 ∘ C can be considered as a mixture of tetra-and nonatitanates; thus they are expected to possess intermediate dielectric properties.…”

“…Conventional method for the preparation of BaTi 4 O 9 is the solid state ceramic route by ball milling of 2 Journal of Nanomaterials stoichiometric amounts of BaCO 3 and TiO 2 for about 24 hours [3,4] and sintering at about 1100 ∘ C. It is then again ball milled, pelletized, and sintered at about 1350 ∘ C to achieve densification of the ceramic body. Wet chemical methods, such as oxalate [5] and citrate route [6] as well as modified Pechini method [7], were also applied for BaTi 4 O 9 powders preparation. Cernea et al [5] obtained BaTi 4 O 9 from oxalates and documented its stable dielectric properties: dielectric permittivity = 38, quality factor = 3800÷4000 at 6÷7 GHz, and temperature coefficient = 11 ppm/ ∘ C. Pure BaTi 4 O 9 suffers from relatively high values of temperature coefficient, so it is not very suitable as dielectric resonator.…”

“…Wet chemical methods, such as oxalate [5] and citrate route [6] as well as modified Pechini method [7], were also applied for BaTi 4 O 9 powders preparation. Cernea et al [5] obtained BaTi 4 O 9 from oxalates and documented its stable dielectric properties: dielectric permittivity = 38, quality factor = 3800÷4000 at 6÷7 GHz, and temperature coefficient = 11 ppm/ ∘ C. Pure BaTi 4 O 9 suffers from relatively high values of temperature coefficient, so it is not very suitable as dielectric resonator. Hence the dielectric properties of BaTi 4 O 9 phase are often modified by using different additives [8].…”

Structure and dielectric properties of BaTi4O9 thin films for RF-MIM capacitor applications

“…In this work, a thin film of BaTi 4 O 9 microwave dielectric ceramics was grown and its structure and dielectric/electrical properties were investigated, in order to evaluate its potential use in RF MIM capacitors. BaTi 4 O 9 ceramics were selected because of their excellent microwave dielectric properties with high k value of 36-38, high Qvalue of 3500-5000 at 6-10 GHz and good thermal stability [11][12][13].…”