Pure and barium fluoride doped potassium yttrium fluoride materials were synthesized using the solid state reaction method and were characterized by X-ray diffraction, transference number and transient ionic current measurements. In all the samples the conductivity was found to be mainly ionic while the electronic conductivity was found to be small. Solid state batteries were fabricated in the configuration K/electrolyte/(I-2 + C + electrolyte) with KYF4 and KYF4:BaF2 as the solid electrolytes. Their discharge characteristics were studied for a load of 100 K Omega at 313 K. Open circuit voltage (OCV) and short circuit current (SCC) of the cells range from 2.38 to 2.82 V and 650 to 2340 mu A, respectively. Various cell parameters were evaluated.