Papers by Keyword: Dopants

Abstract: In the present paper (1-x)Pb (Zr_1-yTi_y)O₃ – xPb (Mn_1/3Sb_2/3)O₃ – z at%E system, with E = Pr³⁺, Nd⁵⁺ and Gd³⁺ where x = 0.12; y = 0.48; z = 0 and 0.02 ceramic synthesized by solid state reaction technique is analysed. The investigation aims studying of the effect of dopants on the dielectric and piezoelectric properties of such piezoelectric ceramic. The prepared powders have been uniaxially pressed into discs with diameter of 10 – 12 mm and thickness of 1.2 mm. Sintering has been carried out in air atmosphere at temperatures of 1150^°C and 1200^°C, respectively, for 2 hours each, followed by a controlled cooling at a rate of 200^°C /h. The piezoelectric properties have been investigated after a suitable preparation, including polishing, metallization. The structure of the samples has been determined by X-ray diffractometry (XRD), while the morphology and grains size have been investigated by the scanning electron microscopy (SEM). The piezoelectric properties have been studied by the resonance - antiresonance method. XRD analysis reveals a perovskite tetragonal structure and, as expected for ceramic materials, SEM analysis indicates that the average grain size increases as sintering temperature increases. The dielectric and piezoelectric properties have been determined measuring the ceramic discs, and properties, as dielectric permittivity (ε_r), dielectric loss (tg δ), and the electromechanical coupling factor (k_p) have been obtained. The acquired results indicate a significant effect of the dopants on the dielectric and piezoelectric properties of such materials.

Abstract: Work related to the development of metal composite materials using effect of super-deep penetration (SDP) of powder particles. Composite materials are obtained from usual casting billets. During SDP process powder particles work as needles and the fibers are formed in metal matrix under dynamic interaction between powder particles and matrix material. Researchers showed high non-uniformity of the chemical composition of the processed material. Material was doped with a high amount of alloying elements at SDP. It may explain specific mechanical and chemical properties of the structure of this new composite material.

Abstract: Ceramic materials present interesting properties and generate products that meet engineering requirements referring to this class for several applications. Aluminum oxide is a very good example of this class of materials, being applied widely in high technology areas especially where the abrasive and erosive wear are strongly demanded. Many factors interfere on the wear of alumina: material composition, characteristics of the used oxides, and the manufacturing process that defines the final microstructure. It is know that the grain size of the alumina has a strong influence on the wear rate and is the focus of several studies. The grain growth during sintering as well as the diffusion process can be controlled by using dopants in the alumina composition. Thus the aim of this paper is to present a review about the dopants interference on the grain size of alumina, which in turn influences the wear behavior of the alumina. The results described allow broad understanding on the subject

Abstract: The effects of the complex donor and acceptor additives on the microstructure, piezoelectric and dielectric properties of PZT (Zr/Ti=53/47) ceramics were studied. A complex doping with the soft (La⁺³ and Nb⁺⁵) and hard (Fe⁺³ and/or Mn^{(+2,+3 or +4)}) ions has been adopted. The complex doping of two or more elements is expected to combine the properties of donor and/or acceptor doped PZT, which could exhibit better stability or improved piezoelectric properties than those of the single element doped PZT. The complex doping caused various compensation effects for the piezoelectric properties of PZT ceramics; Mn addition to the La/Nb and Fe doped PZT composition led to the improved piezoelectric properties, i.e., enhanced Q_m with remaining considerably high k_P.