Abstract: We considered the spatial properties of a class of thermoelastic plates with biharmonic operators. By constructing an energy function and using the technique of differential inequality, we derived a differential inequality in which the energy function could be controlled by its first derivative, and gave the Phragmén-Lindelof alternative result of the solution.

Key words: thermoelastic plate, Phragmén-Lindelof alternative, Saint-Venant principle, biharmonic equation