A new range of stable  solid solutions was found in the system, Li4SiO4-Li3CrO4. These were of the form, Li3+xSixCr1-xO4, where x was between 0.3 and 0.65. When x was between 0 and 0.4, a range of solid solutions that was based upon Li3CrO4 also formed. When x was less than 0.5, the solid solutions were mainly electronic conductors but, with increasing x-value, the electronic conductivity decreased and the materials became either mixed or ionic conductors; depending upon the composition. Thus, a material with x = 0.7 exhibited a Li ion conductivity of 1.7 x 10-6S/cm at 25C. These materials were suggested to be the first examples of mixed conduction in a LISICON-related  solid solution series. A new qualitative method for investigating transport numbers in mixed conductors was proposed, in which direct-current polarization measurements were made by using pelletized samples with Au electrodes, and the amount of charge which was stored as a result of electrochemical decomposition of the pellet was estimated. The results which were obtained from these charge/discharge experiments confirmed those which were obtained by means of low-frequency alternating-current impedance studies.

H.H.Sumathipala, M.A.K.L.Dissanayake, A.R.West: Journal of the Electrochemical Society, 1995, 142[7], 2138-43