Structural and electrical properties of BZT-added BNLT ceramics

Lead free piezoelectric ceramics (1−x)BNLT−xBZT with x=0.00, 0.06, 0.09 and 0.12 were prepared using a two-step mixed oxide method. Dielectric, ferroelectric and piezoelectric properties of the ceramics were improved by the addition of the BZT. XRD results show tetragonal symmetry structure of the BNLT–BZT ceramics. It was found that the tetragonality increases with increasing BZT content. The optimum composition is x=0.09, where the maximum values of the piezoelectric constant d₃₃ (~126 pC/N) and dielectric constant (~2400) were obtained at room temperature. This BNLT–BZT system can be a promising candidate for lead-free piezoelectric ceramics.     

Enhanced electrical properties of lead-free BNLT–BZT ceramics by thermal treatment technique

Electrical properties of lead-free solid solution ceramics from the Bi_0.4871Na_0.4871La_0.0172TiO₃ (BNLT) and BaZr_0.05Ti_0.95O₃ (BZT) system have been improved by a thermal treatment technique. A modified two step mixed-oxide method was employed for the preparation of the (1?x)BNLT–xBZT ceramics, where x=0.06, 0.09, 0.12 and 0.20. After sintering at 1125 °C for 4 h, the BNLT–BZT ceramics were annealed at 825, 925 and 1025 °C. The annealing treatment caused an increase in dielectric constant of BNLT–BZT ceramics with x≤0.09 mol% and with x higher than 0.09 mol% the dielectric value dropped considerably. The ferroelectric properties of all annealed ceramic samples tend to decrease with increasing annealing temperature as confirmed by the slimmer P–E loops. The piezoelectric coefficient (d₃₃) increased with annealing temperatures and a maximum value of ～170 pC/N was obtained from the ceramic samples annealed at 1025 °C with x=0.02.     

Ionic conductivity in samarium-doped NaCl

A study of ionic conductivity as a function of temperature has been carried out in NaCl and NaCl doped with 0.5 and 1.0 mol% samarium. The conductivity-temperature plot of NaCl exhibits a well-known three-stage conductivity in the temperature range 100 to 650° C. The knee separating intrinsic and extrinsic regions is at a temperature of about 525° C. The conductivity-temperature plots of samarium-doped NaCl exhibit three-stage extrinsic (II, III and IV) conductivity in the temperature range 100 to 525° C. The intrinsic region I, was not observed in these plots, as the conductivity measurements were taken up to 525° C. From the analysis of these plots activation energies for the migration of cation vacancy, the formation of Schottky pairs, the association of the samarium ion with a cation vacancy and the dilution of samarium ions in the lattice of NaCl are calculated. These values are compared with previously reported ones.     

Influence of Ca substitution on microstructure and electrical properties of Ba(Zr,Ti)O3 ceramics

In the present work, lead-free (Ba_1?xCa_x)(Zr_0.04Ti_0.96)O₃ (x=0.00–0.09) ceramics were fabricated via a solid-state reaction method. The microstructure and electrical properties of the ceramics were investigated. The microstructure of the BCZT ceramics showed a core shell structure at compositions of x=0.03 and 0.06. The substitution of small amount of Ba²⁺ by Ca²⁺ resulted in an improvement of the piezoelectric, dielectric and ferroelectric properties of the ceramics. The orthorhombic–tetragonal phase transition was found in the composition of x≤0.03. Piezoelectric coefficient of d₃₃～392 pC/N and lowest E_c～3.3 kV/cm with highest P_r～14.1 μC/cm² were obtained for the composition of x=0.03 while its Curie temperature (T_C) was as high as 125 °C. However, the ferroelectric to paraelectric transition temperature had slightly shifted towards room temperature with increasing Ca²⁺ concentration.     

Effects of GeO2 addition on physical and electrical properties of BaFe0.5Nb0.5O3 ceramic

This paper presents the effect of GeO₂ glass former on the physical and electrical properties of BaFe_0.5Nb_0.5O₃ (BFN) perovskite ceramics. The BFN powder was prepared by a conventional mixed-oxide method and the GeO₂ contents, ranging from 1 to 5 wt.%, were subsequently added to the calcined BFN powder. The mixtures were pressed and sintered to form dense ceramics. We showed that, with the addition of GeO₂, the maximum density was achieved at lower sintering temperature, approximately 200–225 °C lower than those required by the pure BFN ceramic. However, the densities of these GeO₂ doped BFN ceramics were slightly lower than those of pure BFN due to the occurrence of pores. We also found that the addition of GeO₂ reduces the dielectric loss at room temperature from 4.29 to 0.39–0.79 but the dielectric constant at room temperature decreased with the increased GeO₂ concentrations. With small amount of added GeO₂, ferroelectric property of BFN ceramics was also obtained, as confirmed by their hysteresis loops.     

Effect of Detonation-Sprayed Cr3C2 and Ni – Cr Coatings on Performance Properties of Gray Cast Iron Gears

Metal Science and Heat Treatment - The microstructure, hardness and wear resistance of gray cast iron with detonation-sprayed Cr3C2 and Ni – Cr coatings are studied. It is shown that the...     

Sol–gel grown Pd modified WO3 thin film based methanol sensor and the effect of annealing temperatures

In this paper, Pd modified WO₃ thin film methanol sensor has been developed by sol–gel method. WCl₆ chemical compound is used as a precursor. Spin coating method is employed for the preparation of the WO₃ thin film on the Si substrate. The crystalline structure of the WO₃ thin film is analyzed by scanning electron microscopy and X-ray diffraction techniques. The thin film sensor is fabricated at different annealing temperatures (400, 600 and 800 °C). The response magnitude of the WO₃ thin film is studied at different operating temperatures (100–300 °C). It is observed that the operating temperature of Pd modified thin film sensor is 200 °C. It is also noticed that the maximum response magnitude of Pd modified WO₃ thin film sensor is found at the annealing temperature of 600 °C. It is found that Pd modified WO₃ thin film sensor are suitable for methanol vapour detection compare to unmodified WO₃ thin film senor.

     

Studies on Recharging of Abrasives in Abrasive Water Jet Machining

The objective of this work is to find the effect of the recharging of local garnet abrasives (origin: southern India) while cutting aluminium using abrasive water jet machining. The influence of the specially formulated optimised abrasive test sample, pressure, traverse rate, and abrasive flowrate, on the American Foundrymen’s Society fineness number, depth of cut, top and bottom kerf width, kerf taper, and surface roughness are studied. The performance of the test sample has been compared with that of commercial grade abrasive with mesh size 80. Additionally, recharging studies are carried out after screening out particles of less than 90 μm. These tests help to determine the optimum recharging required.