Structural Integrity and Microstructure of NA$^{+}$ Conducting Ceramics*

Oxides with the general formula of Na$_{1+x }$Zr$_{2 }$Si$_{x}$ P$_{3-x }$O$_{12 }$, known as Nasicon, are fast Na+ ion-conducting materials with important electrochemical applications and many functional properties, often attributed to their unique structural features. Comparative, in situ studies of the limits of structural integrity were performed for selected Nasicon materials, using synchrotron x-ray diffraction and diamond anvil cell technology. We show how different processing conditions produce crystalline structures with specific morphology. We discuss the bulk modulus, the compressibility and the influence of the volume fraction of primary and secondary crystalline phases on the overall Nasicon structural integrity.