  The measured value of effective electric permittivity \varepsilon_{eff} of
several compounds, e.g., (BiNa)(MnNb)O_{3}, (BiPb)(MnNb)O_{3}, and BiMnO_{3}
increases from a value \approx 10-100 at the low temperature range (100-300 K)
up to the high value reaching the value 10^5 at high temperature range, e.g.,
500-800 K. Such features suggest the manifestation of thermally activated space
charge carriers, which effect the measured capacitance. The measured high-value
effective permittivity of several manganite compounds can be ascribed to the
chemical capacitance C_{\mu}=e^2\partial N_{i}/\partial \mu_{i} expressed in
terms of the chemical potential \mu. The chemical capacitance C_{\mu}^{(cb)} =
e^2 n_{C}/k_{B}T depends on temperature when the conduction electrons with
density n_{C} = N_{C} \exp(\mu_{n}- E_{C})/k_{B}T are considered. The
experimental results obtained for the manganite compounds, at high temperature
range, are discussed in the framework of the chemical capacitance model.
However, the measured capacitance dependence on geometrical factors is analysed
for BiMnO_{3} indicating that the non-homogeneous electrostatic capacitor model
is valid in 300-500 K range.
