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Polycrystalline ceramics in (1 − x)K1/2Na1/2NbO3 − xCaZn1/3Ta2/3O3 (abbreviated as KNN-CZT) solid solution have been fabricated by using conventional solid-state synthesis route and the effect of CZT addition on the crystal structure, dielectric, and piezoelectric behaviour of KNN has been studied. Rietveld refinement of the room temperature X-ray diffraction data confirmed the crystal structure to be a pure perovskite phase for the compositions in the range x = 0 − 0.10. Further, the crystal structure gradually changed from orthorhombic to cubic via the formation of rhombohedral and tetragonal mixed phases with the increase in x. Raman spectroscopy suggested damping of phonon modes and a strong anharmonicity in the crystal arising due to the increased disorder in the structure as a consequence of multivalent cations occupying the A and B sites in CZT substituted compositions. Dielectric behaviour indicated the shifting of both tetragonal-cubic and orthorhombic–tetragonal phase transitions towards room temperature. The temperature dependent dielectric constant was modelled by Lorentz quadratic law, and the fitted value of diffuseness parameters confirmed an increase in diffuseness of phase transition with increasing substitution. Sample with the composition corresponding to x = 0.02 showed an improved piezoelectric coefficient d33 ~ 125 pC/N and electromechanical coupling coefficient kp ~ 30% at room temperature and d33 ~ 61 pC/N and kp ~ 24% at 300 °C which make this material a potential candidate for high-temperature piezoelectric applications. Variation of voltage coefficient (g33) with the change in compositions are also reported. Improvement in the piezoelectric properties is attributed to the reduced oxygen vacancies. [ABSTRACT FROM AUTHOR]

Surface roughness is one of the critical parameters that affect the component performance during its working life. To develop any process to its full potential, it is necessary to understand the physics of that process. Abrasive flow finishing (AFF) is one of the advanced finishing processes. In the current research work, an effort is made to understand physics and mechanism of surface roughness improvement during the AFF process. This research paper is divided into two sections. Firstly, the amount of finishing stresses and forces generated during the finishing of microholes fabricated on surgical stainless steel (316L) workpieces are computed by using the finite element method. Finishing stresses are generated in the viscoelastic medium. So, to compute finishing stresses, finite element analysis of the viscoelastic medium is carried out by incorporating its experimentally measured rheological properties. Finishing stresses are calculated along the circumferential direction of the microhole. Later, at the same workpiece surface location, simulated and experimentally measured surface roughness value are compared. Secondly, a new simulation model is proposed to predict the surface roughness on the microhole wall surface for various AFF input parameters. Maximum percentage change in surface roughness error of 8% is observed between simulated and experimental results after AFF process. [ABSTRACT FROM AUTHOR]