Effect of chemical composition on microstructural properties and sintering kinetics of (Ba,Sr)TiO3 powders

Abstract

Barium strontium titanate powders with different Ba:Sr ratios were investigated to determine the influence of the initial composition of powder mixture on microstructural properties and sintering kinetics. It was determined that BaCO 3 and SrCO 3 react differently to mixing, resulting in Ba 0.5 Sr 0.5 CO 3 in the sample with 80% Ba and different contents of Ba 1-x Sr x TiO 3 in samples with 50% and 20% Ba. In addition, the morphology is also different, with higher Sr content leading to larger particles size and less agglomeration. The different chemical content of the initial powder mixture also has a marked impact on the sintering process: the onset of sintering shifts towards higher temperature with higher Sr content, while the average apparent activation energy of sintering is the highest for the sample with 80% Ba and the lowest for the mixture with 50% Ba. In addition, hexagonal-to-cubic phase transformation was observed in parallel with the sintering process, where the position of the phase transition shifts to lower temperatures with an increase in Sr content. This is consistent with the behavior of low-temperature phase transitions of BST. The phase transition was not observed in sintered samples, suggesting that there is a size-dependence of the phase transition temperature.

Analysis of the initial-stage sintering of mechanically activated SrTiO3

“…The density of samples STO0 and STO10 does not change noticeably until the temperature reaches value of around 1100 o C, while it rapidly increases above 1230 o C. In the case of samples STO30 and STO120, density begins to gradually increase at lower temperatures (around 750 and 550 o C, respectively), with a sharp rise above 1200 o C. The final densities, obtained after non-isothermal annealing up to 1300 o C and isothermal holding at this temperature for 2 h, were higher for the STO10 (ρ ~ 4.08 g/cm 3 ) and STO30 (ρ ~ 4.04 g/cm 3 ) samples, compared to the STO120 (ρ ~ 3.96 g/cm 3 ) and STO0 (ρ ~ 3.59 g/cm 3 ) samples. Fig.…”

“…In the fabrication process of the advanced electroceramics materials, preparation conditions, and especially sintering, are important factors which can significantly affect the mechanical and functional properties of these materials [1,2]. Strontium-titanate (SrTiO 3 ) is a very attractive functional electroceramic material because of its remarkably high dielectric permittivity, tunability and low microwave loss [3,4]. The high dielectric constant of SrTiO 3 allows its usage in high-storage-density capacitors (dynamic random access memory-DRAM), and various microwave devices [5][6][7].…”

Local hardening of Raman phonons in BaxSr1−xTiO3 thin films deposited by r.f. sputtering

“…The inset (a) does not show the (002) XRD peak at lower 2θ values, next to the (200) one for all the x values, which indicates that the films are constituted only by the cubic phase [17,18]. The inset (b) shows two small peaks, pointed out with asterisks, sited in the 552θ75°interval, which were discarded as coming from other BSTO phases, these signals more probable are impurities that were originated by carbon-based oxides from the chamber ambient [19,20].…”

Characterization of MgAl2O4 sintered ceramics

“…8 %) associated with spinel phase formation from alumina and magnesia inhibits formation of dense bodies in a single-stage reaction sintering process [24]. Also, as the time of mechanical activation increased, the temperature corresponding to the onset of shrinkage noticeably decreased from ~ 1409 °C in AM-0 to ~ 1340 o C in AM-120 [32,33]. Furthermore, with the prolonged mechanical activation, the apparent decrease in expansion was due to the lower energy needed for spinel reaction [18].…”