Q.Temperature characteristics guide (7): How much change in capacitance with temperature can I expect?
Capacitors > Ceramic Capacitors > Multilayer Ceramic Chip Capacitors
C0G and NP0 Class 1 ceramic temperature characteristics do not show significant changes in capacitance vs temperature.
Generally, heat lowers Class 2 capacitors' capacitances, however around the Curie point (approximately 120°C for BaTiO3), the capacitance increases. This is due to an increase in the dielectric constant as the crystal structure of the ceramic changes from tetragonal to cubic.
The EIA and JIS standards state that within the operating temperature range, the change in capacitance will not exceed the specified tolerance. The chemical composition of the ceramic is not a part of the standard. Manufacturers of capacitors use different additives to the dielectrics in order to change the performance of the capacitors. These additives can shift the Curie point closer to room temperature (e.g. Z5U) or smooth the dielectric constant curve (e.g. X7R). The former have the highest unbiased dielectric constants, while the latter lower the maximum dielectric constant in order to achieve greater temperature stability.
These formulations are proprietary, and ensure that not all capacitors are created equal.
Below is a graph of several MLCC's temperature characteristics.