Solid solutions based on rubidium pyrophosphate are synthesized in the Rb4-
2xMxP2O7 systems (M = Ca, Sr, Ba, Ph). The temperature and concentration de
pendences of their rubidium-cation conductivity are investigated. The X-ray
data for the low- and high-temperature forms of Rb4P2O7 and also for solid
solutions based on it are reported. The effect exerted by modifying cation
M2+ on electrical properties of synthesized solid solutions is considered.