The scheelite-like double tungstate Na5YW4O16 was selected by using Voronoi tessellation as a compound with suitable channels for ionic transport. The effect of charge carrier density on the ionic conductivity was investigated by heterovalent substitution of Ca2+ for Na+ and Y3+. Ionic conductivities of ceramics at 300 degrees C are 3.4 . 10(-5) S/m for Na5YW4O16 and 8.5 . 10(-6) S/m for Na4.6Ca0.2YW4O16. It is proposed to use new term "pathway density" to explain low value of ionic conductivity for the studied compound. (C) 2016 Elsevier B.V. All rights reserved.