Polycrystalline Na2W2O7 (anhydrous) was prepared by a solid‐state reaction technique. The formation of the compound has been confirmed by X‐ray powder diffraction studies and Raman spectroscopy. The unit cell structure of the material has been found to be orthorhombic of the Cmca space group. Complex impedance analysis of the material indicates the electrical conduction to be due only to the grain interior up to a temperature of 300 °C. Above 300 °C the contribution of the grain boundary to electrical conduction is more evident. The grain boundary resistance is found to decrease with increasing temperature. Impedance results also indicate that the material exhibits a negative temperature coefficient of resistance. The electrical processes in the material show temperature‐dependent relaxation phenomena. The electrical conduction in the material is a thermally activated process governed by the release of space charge in close agreement with the observations made from impedance spectrum analysis. The dc conductivity of the material as evaluated from the complex impedance spectrum is observed to attain a maximum value of 1.16 × 10−6 S cm−1 at 425 °C. This is a very large increase, nearly four orders of magnitude, when compared with the room temperature conductivity of the material (3.99 × 10−10 S cm−1). (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Electromigration (EM) is re-emerging as a significant problem in modern integrated circuits (IC). Especially in power grids, due to shrinking wire widths and increasing current densities, there is little or no margin left between the predicted EM stress and that allowed by the EM design rules. Statistical Electromigration Budgeting (SEB) estimates the reliability of the grid by considering it entirely as a series system. However, a power grid with its many parallel paths has much inherent redundancy. In this work, we propose a new model to estimate the MTF and reliability of the power grid under the influence of EM, which accounts for these redundancies. We refer to this as the mesh model.To implement the mesh model, we also develop a framework to estimate the change in statistics of an interconnect as its effective-EM current varies. The proposed algorithm is quite fast and has an overall observed empirical complexity of O(n 1.5−1.6 ). The resultsindicate that the series model, which is currently used in the industry, gives a pessimistic estimate of power grid MTF and reliability by a factor of 3-4.ii

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