Effect of ZnO on sintering and microwave dielectric properties of 0.5CaTiO3-0.5 (Li0.5La0.5) TiO3 ceramics

The novel calcium titanate-lithium lanthanum titanate doped with zinc oxide (0.10, 0.30, and 0.50 mol. %) ceramic samples were prepared by solid-state reaction route. The phase formation, microstructure, densification, and microwave dielectric properties were investigated. It was found that the doping with zinc oxide led to a decrease in sintering temperature by 25 ^oC as compared with pure calcium titanate lithium lanthanum titanate due to the liquid phase effect. Also, the calcium titanate lithium lanthanum titanate (10ZCTLLT&30ZCTLLT)) doped with lower zinc oxide (0.10 and 0.30 mol. %) led to higher densification parameter. This was followed by increasing the zinc oxide doping up to (0.50 mol. %) which resulted in a decrease in densification and microwave dielectric properties which may be attributed to increase in porosity and grain growth upon the evaporation of zinc and oxygen vacancy. This led to the increase in dielectric loss (≈10 × 10^?4) value with 50ZCTLLT. Hence, the best result of microwave dielectric characteristics was obtained for 0.5CaTiO₃–0.5(Li_0.5La_0.5)TiO₃ with (0.10 and 0.30 mol. % ZnO) 10ZCTLLT and 30ZCTLLT ceramic samples sintered at 1175 ^oC/2h, with low dielectric constant (ε_r) = 4.4–10.5, very low dielectric loss = 1.07-2.23 × 10^?4 and high quality factor (Q x ?) ≈59-55 × 10⁴ at 8 GHz. Consequently, they can be used not only in wireless satellite communications technology but also can be used in the fifth-generation telecommunication 5G technology construction.     

Application of BaTiO3-based catalysts for piezocatalytic,photocatalytic and piezo-photocatalytic degradation of organic pollutants and bacterial disinfection in wastewater: A comprehensive review

The coupling of piezocatalysis and photocatalysis known as piezo-photocatalysis has attracted a lot of attention as one of the most effective advanced oxidation process (AOPs) for wastewater treatment, especially for the degradation of organic pollutants and disinfection of microbes. To advance this technology, there’s a need to develop lead free piezoelectric materials to drive both piezocatalytic and photocatalytic process to prevent secondary pollution due to lead toxicity. Hence, barium titanate (BaTiO₃) has been widely used as lead free piezoelectric material for several applications including water splitting, bacterial disinfection, and wastewater treatment due to its exceptional optical and piezoelectric properties. This work presents a comprehensive review on the application of BaTiO₃ as a promising lead-free piezo-photocatalyst for the catalytic degradation of organic pollutants and bacterial disinfection from aqueous solution. This review article details the optical and piezoelectric properties, modification strategies, and synthetic methods of BaTiO₃. Furthermore, the application of BaTiO₃ as a preferred piezo-photocatalyst for wastewater treatment and a future perspective is presented.     

Uniaxial stress dependence of the dielectric properties of barium titanate single crystals

BaTiO₃ single crystals were grown by the melt-grown method. The effect of uniaxial pressure (0–1700 bar) on the dielectric properties of these crystals has been systematically studied. The external stress showed obvious effects on these properties. An increase in the difference between the Curie T_c and Curie–Weiss T₀ temperatures induced by the applied pressure is observed. This could be ascribed to the inducing of non-ferroelectric cubic islands in the tetragonal phase by the applied compressive stress. On the other hand, the pressure behavior of thermal hysteresis and the ??/?T vs. T plot strongly suggests that the phase transition changes to second-order type with increasing pressure. The Curie–Weiss constant obtained from a modified Curie–Weiss law strongly decreases with increasing pressure, suggesting that the mechanism of phase transition is going to order–disorder type. An increase in the difference between the Curie T_c and Burn's T_B temperatures with increasing pressure is observed. This could be ascribed to the narrowing of the temperature range on which the Curie–Weiss law is valid. In general, the obtained results are in good agreement with hydrostatic pressure data. Some kind of relaxation near T_c, which is strongly coupled with strain caused by applied compressive stress, is postulated.     

Preliminary results on sol-gel processing of 〈100〉 oriented Pb(Mg<Subscript>1/3</Subscript>Nb<Subscript>2/3</Subscript>)O<Subscript>3</Subscript>-PbTiO<Subscript>3</Subscript> thin films using diol-based solutions

A novel sol-gel method is used here for the synthesis of air-stable and precipitate-free diol-based sols of 0.7Pb(Mg_1/3Nb_2/3)O₃-0.3PbTiO₃ (PMN-PT). Sols containing a 15 mol% lead excess have been used for the preparation of PMN-PT thin films. The films were deposited onto (111)Pt/TiO₂/SiO₂/(100)Si substrates, and crystallised in oxygen by Rapid Thermal Processing (RTP), using different temperatures and soaking times. Single perovskite films are obtained when treated at temperatures between 600 and 700°C for 6 s. Those crystallised at other temperatures contain a secondary pyrochlore phase. This phase also appears in the films treated at 650°C with soaking times longer than 6 s. PMN-PT films with a 〈100〉 preferred orientation were prepared by using a PbTiO₃ seeding layer onto the substrate. These PMN-PT films present relaxor-type electrical properties. Dielectric permittivity, , shows significant dispersion. Its temperature dependence presents a broad maximum at 110–130°C, which position shifts towards higher temperatures with frequency. Ferroelectric hysteresis loops show high values of saturation polarisation but very low remanence. The piezoelectric activity of the films has been tested by the measurement of their local piezoelectric hysteresis loops.     

均分散胶体的研究(Ⅳ)——钛酸锶均分散粒子的制备

烧制电子陶瓷用的SrTiO_3粉料不仅要求纯度高,而且对粒子的尺寸及均匀性也有严格要求。目前虽可用喷雾沉淀等方法制得尺寸为微米级的SrTiO_3粒子,但其形状与尺寸很不规整。用通常的均分散体系制备方法曾制得均分散BaTiO_3粒子,但由于制备溶液的浓度太低,难以实现工业化。其实,反应溶液浓度低、反应时间长、控制条件严格是大规模制备均分散粒子的共同弱点。本工作提出了一种简便、快速制备均分散SrTiO_3粒子的方法,有望实现均分散粒子制备的工业化。     

二溴对甲基偶氮溴羧与钡显色反应的研究与应用

研究了新显色剂二溴对甲基偶氮溴羧与钡显色反应的条件。在磷酸介质中,试剂与钡形成2:1的络合物,最大吸收波长为610nm,摩尔吸光系数为2.13×10~4L·mol~(-1)·cm~(-1),钡量在0～20μg/25ml范围内符合比耳定律。两倍的锶和五倍的钛不干扰,钙的允许量较大,方法用于直接测定钛酸钡烧结物中微量钡,结果满意。     

掺希土离子Eu3+的BaTiO3超细微粉的制备及物性表征

近年来人们对材料及由材料制备的元件提出了高可靠性、多功能等要求。为了达到这种要求,人们从多种途径进行了探索,其中,对现有材料进行掺杂就是很有效的方法之一［１,２］。本文报道对ＢａＴｉＯ３超细微粉进行Ｅｕ３＋的有效掺杂并对其进行了物性表征。１实验部分１...     

Lead zirconate titanate cantilever for noncontact atomic force microscopy

Noncontact atomic force microscopy with frequency modulation detection is a promising technique for surface observation with true atomic resolution. The piezoelectric material itself can be an actuator and sensor of the oscillating probe simultaneously, without the need for additional electro-mechanical transducers or other measurement systems. A vertical resolution of 0.01 nm rms has been achieved using a microfabricated cantilever with lead zirconate titanate thin film in noncontact mode frequency modulation detection. The cantilever also has a sharpened pyramidal stylus with a radius of about 10 nm for noncontact atomic force microscopy.     

Raman Spectroscopic Investigation of the Stress State in Silicon Substrates near Edges of Pt/PZT Microstructures

Hydrostatic stresses in Si substrates near edges of Pt/PZT microstructures used in pyrosensor fabrication have been predicted theoretically by finite element (FE) calculations. Within the absorption limited depth zone from which Raman radiation can be detected the substrate stress varies considerably. The characteristic lateral length scale of the average stress profile perpendicular to the film edges is less than 50 μm resulting from contributions of different depth. These stresses could be measured by spatially resolved Raman spectroscopy with an accuracy of 1‐2 μm.The values of the film stress of Pt and PZT have been estimated by fitting the FE models to the measured curves of the stress distribution in the Si substrate.     

Li mobility in Li0.5 − xNaxLa0.5TiO3 perovskites (0 ≤ x ≤ 0.5): Influence of structural and compositional parameters

The dependence of Li mobility on structure and composition of Li_0.5 − xNa_xLa_0.5TiO₃ perovskites (0 ≤ x ≤  0.5) has been investigated by means of neutron diffraction, nuclear magnetic resonance and impedance spectroscopy. At 300 K, all samples display a rhombohedral superstructure (R-3c S.G.), where octahedra are out of phase tilted along [111] direction of the ideal cubic cell. The elimination of the octahedral tilting is responsible for the rhombohedral–cubic transformation, detected near 1000 K. In these perovskites, La and Na cations are randomly distributed in A sites, but Li ions are fourfold coordinated at unit cell faces of the cubic perovskite. Lithium conductivity, σ_300 K, decreases with the sodium content, decreasing from values typical of fast ionic conductors, 10^− 3 S/cm, to those of good insulators, 10^− 10 S/cm, when the interconnectivity between vacant A sites is lost (x > 0.3). In samples with x < 0.3, dc conductivity displays a non-Arrhenius behaviour, decreasing activation energy from ~ 0.37 to 0.25 eV when the sample is heated between 77 and 500 K. The temperature dependence of B_Li factors shows the existence of two regimes for Li motion. Below 373 K, Li ions remain partially located near square oxygen windows that connect contiguous A sites, but above 400 K, extended Li motions become dominant. The additional decrease of activation energy from 0.25 to 0.16 eV (low-temperature ⁷Li NMR value), should require the full elimination of octahedral tilting which is only produced above 1000 °C.