The specific heat capacity of LAGP materials with general formula  fits into the Maier-Kelley polynomial law in the temperature range from room temperature to 700 °C:
where
: is the absolute temperature,
:  are fitting constants.
Typical values are in the range of 0.75 - 1.5 J⋅g⋅K in the temperature interval 25 - 100 °C. The  constants increase with the x value, i.e. with both the aluminium and the lithium content, while the constant  does not follow a precise trend. As a result, the specific heat capacity of LAGP is expected to increase as the Al content grows and the Ge content decreases, which is consistent with data about the relative specific heats of aluminium and germanium compounds.
In addition, the thermal diffusivity  of LAGP follows a decreasing trend with increasing temperature, irrespective of the aluminium content:
The aluminium level affects the exponent , which varies from 0.08 (high Al content) to 0.11 (low Al content). Such small values suggest the presence of a large number of point defects in the material, which is highly beneficial for solid ionic conductors. Finally, the expression for the thermal conductivity can be written:
where
: is the heat capacity per unit volume, 
: is the average phonon group velocity,
: is the phonon mean free path,
: is the density of the material.
Taking everything into account, as the aluminium content in LAGP increases, the ionic conductivity increases as well, while the thermal conductivity decreases, since a larger number of lithium ions enhances the phonon scattering, thus reducing the phonon mean free path and the thermal transport in the material. Therefore, thermal and ionic transports in LAGP ceramics are not correlated: the corresponding conductivities follow opposite trends as a function of the aluminium content and are affected in a different way by temperature variations (e.g., the ionic conductivity increases by one order of magnitude upon an increase from room temperature to 100 °C, while the thermal conductivity increases by only 6%).