Papers by Keyword: Lead-Free

Abstract: The X-ray diffraction, microstructure, impedance, electric modulus, and ac-conductivity of Ba(Fe_1/2Ta_1/2)O₃–(Na_1/2Bi_1/2)TiO₃ solid-solutions were studied utilising a traditional high-temperature mixed-oxide technique. The phase-formations of the solid-solutions were determined utilising X-ray data, while SEM micrographs revealed a non-uniform dispersion of grains in the sample of unequal size (~1 – 20 mm). In all of the developed solid-solutions, the frequency (1Hz - 1MHz) dependence of imaginary and real parts of electric impedance in the temperature region of 50 and 500°C showed the NTCR character and hopping type of electrical conduction. The modulus spectrum variation was intrigued by the hopping mechanism for charge transport (temperature-dependent) in the samples with non-Debye type of behaviour. Besides, the low electrical conductivity of these solid-state solutions makes them ideal for industrial applications, particularly as capacitors.

Abstract: The microstructure, energy dispersive X-ray spectra, and field dependent polarization and electrostrictive strain characteristics of x(Ba_0.7Ca_0.3)TiO₃–(1-x)Ba (Zr_0.2Ti_0.8)O₃; x = 0, 0.5, and 1.0 synthesised using solid-state reaction process are discussed in this work. The X-ray diffraction process and scanning electron microscope were, respectively taken into use to examine the forming of single-phase compound and the surface morphology as well as elemental analyses of all of the samples. The grains sizes were found to lie between 3–12 μm and was largest for x = 0.5. The value of piezoelectric coefficient, converse piezoelectric effect (strain maximum to peak electric field), and electrostrictive coefficient were found to be the highest for x = 0.5 sample. Ba_0.85Ca_0.15Zr_0.10Ti_0.90O₃ was shown to be a potential lead-free electrostriction material for industrial applications, particularly in positioning actuators, based on field-dependent polarisation and strain experiments at ambient temperature.

Abstract: The mechanical impact-based energy harvesting behavior of a 0-3 Bi_0.5Na_0.5TiO₃/PVDF(25/75) composite prepared using the melt-mixing method have been demonstrated. X-ray diffraction analyses revealed the formation of a composite sample, while AFM image analyses revealed that BNT-particle sizes ranged between 0.6 and 1.4 μm and were evenly distributed throughout the polymer matrix, and surface roughness was found to be between 0.2 and 1.8 μm. With increasing impact height (applied mechanical energy), a remarkable increase in generated electric voltage and energy was observed. As a result, the present composite is a better lead-free alternative for piezo-sensing/detection and energy harvesting applications.

Abstract: Combining copper alloy with steel back to make bearing bush can not only improve the strength of bearing bush, but also prolong the life of bearing bush, which is called bimetallic bearing. In this paper, the development status of copper alloy materials in bimetallic bearing bushes and the manufacturing principle and characteristics of copper alloy-steel bimetallic bearing bushes are summarized, and the defects of several manufacturing processes are analyzed. This paper summarizes the research on improving the performance of copper-steel bimetallic bearing bush. Finally, the development direction of the preparation process of copper alloy-steel bimetal is prospected.

Abstract: Sr_0.7Bi_0.2TiO₃ (SBT), a kind of lead-free relaxor ferroelectric, is attracting more and more attention for pulse energy storage applications due to the low remnant polarization and high energy storage efficiency (h). However, relatively low dielectric breakdown strength (DBS) limited the recoverable energy storage density (W_rec). Herein, CaTiO₃ with high intrinsic DBS was introduced in SBT. The novel solid solutions (1-x)SBT-xCT with x = 0 - 0.15 shows pure pseudo-cubic perovskite structure. When x = 0.05, the maxium polarization are improved, and the CT doping decreases the average grain size, leading to an enhanced DBS. A high energy storage properties of 1.59 J/cm³ with the h of 87.4% at 220 kV/cm is achieved in 0.95SBT-0.05CT, which demonstrates that this 0.95SBT-0.05CT is prospective materials for energy storage application.

Abstract: The lead-free wood leafhopper is the iconic traditional ceramic art of the Jizhou kiln in the Song Dynasty of China. The traditional lead-free wood leafhopper is usually made of black glaze. The glaze is placed on the mulberry leaf and fired at a high temperature of about 1230 °C-1260 °C. And the veins are clear. Jizhou kiln was founded in the late Tang Dynasty. It flourished in the Five Dynasties and Northern Song Dynasty. It was the most prosperous in the Southern Song Dynasty. It began to decline in the late Yuan Dynasty and then stopped for more than 700 years. However, its unique artistic value has gradually be attracted the attention by the world. And it recovered in 1985 at last after unremitting efforts. The re-burning of the lead-free wood leafhopper has successfully opened the ceramic market of the lead-free wood leafhopper and made it occupy a certain position in the ceramic market. The price of lead-free wood leafhopper has remained high, and therefore ceramic producers are waiting for opportunities to produce on a large scale in order to achieve huge economic benefits. However, due to the great difficulty in the firing process of the lead-free wood leafhopper, the market has a phenomenon of low yield, high price, low consumer desire, and the use of chemical materials to fire products. The subject analyzed and solved these phenomena through a large number of experiments. Lead-free in this subject is a relatively broad definition, especially referring to the new type of lead-free wood leafhopper without contain heavy metals.

Abstract: Since the environmental regulations of Reduction of Hazardous Substances (RoHS) directive came into effect in Europe and Asia on July 1, 2006, requiring the removal of any lead (Pb) content from the electronics industry, the issue of tin (Sn) whisker growth from pure Sn and SnPb-free alloys has become one of the most imperative issues that need to be resolved. Moreover, with the increasing demand for electronics miniaturization, Sn whisker growth is a severe threat to the reliability of microelectronic devices. Sn whiskers grow spontaneously from an electrodeposited tin coating on a copper substrate at room temperature, which can lead to well-documented system failures in electronics industries. The Sn whisker phenomenon unavoidably gives rise to troubles. This paper briefly reviews to better understand the fundamental properties of Sn whisker growth and at the same time discover the effective mitigation practices for whisker growth in green electronic devices. It is generally accepted that compressive stress generated from the growth of Cu₆Sn₅ intermetallic compound (IMC) is the primary driving force for Sn whisker growth during room temperature storage. It is, therefore, important to determine that the relationship between IMC growth and Sn whisker growth. Reduction of stress in the IMC layer can therefore reduce the driving force for whisker formation and be used as a means for whisker mitigation. To date, there are no successful methods that can suppress the growth of Sn whisker as efficient as Pb addition. It is hoped that the Sn whisker growth mechanisms are understood better in the future, with better measuring and monitoring methodologies and systems being developed, the real solutions may be eventually developed to eliminate or mitigate the Sn whisker problems of green reliability lead-free electronic assemblies.

Abstract: Since the mechanism of Sn-whisker growth is closely related with the behavior of deformation and recrystallization, understanding of the behavior is very important to establish the measure for mitigation of whisker growth. In this work, microstructural changes after heavy deformation by scratching were characterized by EBSD for a single crystal of β-Sn, and the following results were obtained. Three types of crystal grains appear immediately after the deformation; small grains in aggregation, large serrated grains and rim-grains. The small grains are considered to be formed by dynamic recrystallization. They continue to grow at a room temperature over a lengthy period of time. The large grain has a certain crystallographic relationship with the matrix where <100> axes of the large grain and the matrix are almost parallel to each other. The serrated boundaries of large grain are so stable that the large grain does not show a grain growth process. The stable boundary is considered to promote a continuous growth of whiskers.

Abstract: 0.82NBT-0.18ST and 0.85NBT-0.15ST thin films have been prepared on Si substrates by a modified metalorganic solution deposition process. To achieve films with better ferroelectric properties, three main items have been changed in the process. Then the crystal structures, surface microstructures, hysteresis loops, fatigue curves and capacitance-voltage curves of the films were measured. It can be found that NBT-ST films can crystallize well after annealing at 650 °C for 5 minutes and have smooth surface microstructures. The 0.85NBT-0.15ST thin films exhibit better well-defined hysteresis loops than 0.82NBT-0.18ST, with a remnant polarization of 1.1 mC/cm² and a coercive fields of 44.2 kV/cm. The clockwise C-V curves show that they have a desired polarization-type switching mode. The memory window of 0.82NBT-0.18ST thin film is about 1.8V, and that of 0.85NBT-0.15ST thin film is about 2.5V.

Abstract: Lead-free EO ceramics have been received increasing attentions from the view point of green environment in recent years. In this study, lead-free Ba_6-1.5xLa_xTi₂Nb₈O₃₀ (0≤x≤7%) ceramics were synthesized by the conventional solid state reaction sintering method. The effects of lanthanum doping on the microstructure and electrical properties of Ba₆Ti₂Nb₈O₃₀ (BTN) ceramics were investigated and analyzed. The XRD results revealed that the lanthanum doping changed the BTN lattice parameters slightly. The sample grain size, dielectric constants (1kHz) and the temperature Tm gradually decreased with the increasing of lanthanum doped content. The optimized BLTN ceramic sample with x=4 mol % exhibited a good transparency and excellent electrical properties (Ps=6.41 μC/cm², Pr=0.77 μC/cm², and Ec=3.80 kV/cm).