Effects of A-Site (NaCe) Substitution with Na-Deficiency on Structures and Properties of CaBi₄Ti₄O₁₅-Based High-Curie-Temperature Ceramics

Abstract

Three kinds of bismuth-layer-structured ferroelectric (BLSF) ceramics, CaBi4Ti4O15 (CBT), Ca0.8(CeNa)0.1Bi4Ti4O15 (CNBT), and Na-deficient Ca0.8(Ce0.1Na0.05\Box0.05)Bi4Ti4O15 [CN\BoxBT] (where \Box represents vacancies) were prepared by a conventional ceramic technique. X-ray powder diffraction showed that their crystal structures are a single phase of BLSF with m=4. Sintering characteristics of the three ceramics were also discussed. Scanning electron microscope (SEM) micrographs of CN\BoxBT showed that the grain is platelike. The A-site (NaCe) substitution can improve the piezoelectric constant d 33 and high-temperature resistivity with decreasing Curie temperature. The modification by A-site (NaCe) substitution with Na-deficiency is more pronounced than CNBT, which not only leads to a very high piezoelectric constant d 33 and high-temperature resistivity but also increases the Curie temperature. The reason for the high T c (T c=866°C) of CN\BoxBT is considered to be internal stress. As a result, Na-deficient CN\BoxBT ceramic is found to be an excellent high-temperature piezoelectric material.

Research on the Thermal Aging Behaviors of LDPE/TiO2 Nanocomposites

“…At the same time, it can be seen from Figure 3 that the "oxidation induction period" of Pure-LDPE was 14 days, while that of LDPE/TiO 2 -0.5 was 56 days. The small size effect and surface effect of nanoparticles changed the recrystallization process of LDPE/TiO 2 , generating more small grains and lots of LDPE/TiO 2 interface regions, and consequently the crystallinity of LDPE/TiO 2 is higher compared to Pure-LDPE [6]. So, the oxygen is difficult to diffuse into material and hard to spread quickly inside of material due to compact structure of LDPE/TiO 2 nanocomposites, thereby enhancing the ability of thermaloxidative aging.…”

“…Crystallization behavior of nanocomposites play a crucial role in morphologies and the resulting properties to some extent, and the crystallization is regarded as a naturally self-assembly process [4,5]. In the process, the filler particles and other impurities in the nanocomposites are rejected from the crystal phase and incorporated into the amorphous region [6]. Recently, Zheng et al investigated the structure and morphology of the polyamide-6/ZnO nanocomposites and reported that the ZnO nanoparticles can induce the crystallization of the -crystalline form PA-6 from the melt and during the annealing of the amorphous solid [7].…”

Influences of ScTa co-substitution on the properties of Ultra-high temperature Bi3TiNbO9-based piezoelectric ceramics

“…However, the piezoactivity of pure BTNO ceramics is quite low (d 33 <7 pC/N) [10] for high temperature applications. The A-site substitution or/and B-site substitution have been shown to be effective in modifying the structure and polarization process [11][12][13][14][15][16][17][18][19][20][21][22][23]. Only a few works have addressed the properties of cation-modified BTNO-based ceramics.…”

Кристаллическая структура и диэлектрические свойства слоистых перовскитоподобных твердых растворов Bi-=SUB=-3-x-=/SUB=-Y-=SUB=-x-=/SUB=-TiNbO-=SUB=-9-=/SUB=- (x =0.0,0.1,0.2,0.3) с высокой температурой Кюри

“…Было показано на многочисленных примерах [19][20][21][22][23][24][25][26][27][28][29][30][31], что замены атомов как в A, так и в B-позициях кристал-лической решетки ФА приводят к изменениям структу-ры, диэлектрических свойств и значительно влияет на поляризационные процессы в этих соединениях.…”