A new form of MgTa ₂O ₆ obtained by the molten salt method

Using molten salt route (with NaCl/KCl as the salt) we have been able to synthesize a new form of magnesium tantalate at 850°C. Powder X-ray diffraction data could be indexed on an orthorhombic unit cell with lattice parameters, 'a' = 15·36(1) Å, 'b' = 13·38(1) Å and 'c' = 12·10(1) Å. High resolution transmission electron microscopy and electron diffraction studies confirm the results obtained by X-ray studies. Energy dispersive X-ray spectroscopy helps ascertain the composition of MgTa ₂O ₆. The title compound shows a dielectric constant of ∼24 with a low dielectric loss of 0·006 at 100 kHz at room temperature. Dielectric constant is nearly unchanged with rise in temperature while the loss shows a very marginal increase (0·007 at 300°C).