For plate bending and stretching problems in piezoelectric materials, the reciprocal theorem and the general solution of piezoelasticity are applied in a novel way to obtain the appropriate mixed boundary conditions accurate to all order. A decay analysis technique is used to establish necessary conditions that the prescribed data on the edge of the plate must satisfy in order that it should generate a decaying state within the plate. For the case of axisymmetric bending and stretching of a circular plate, these decaying state conditions are obtained explicitly for the first time when the mixed conditions are imposed on the plate edge. They are then used for the correct formulation of boundary conditions for the interior solution.boundary conditions, piezoelectric plates, mixed data, bending problems, stretching problems As piezoelectric patches used as actuator or sensor are usually considered as plates because of their plate-like geometry, many scientists paid more attention to the study of piezoelectric plates. Tiersten [1] and Mindlin [2,3] initiated the study based on power series expansions of the mechanical displacements and the electric potential along the thickness of the plate and the variational principle, while Bugdayci and Bogy [4] and Lee et al. [5] applied trigonometric series representation to the research of piezoelectric plates. Besides, other scholars, such as Lee [6] , Bisegna and Caruso [7] , and Krommer [8] , performed similar analyses based on classical plate theories or refined plate theories in combination with a gross linear, quadratic or biquadratic through-the-thickness distribution of the electric potential. Recently, by utilizing the general solution of piezoelasticity and Lur'e method, a refined theory for piezoelectric plates was deduced systematically and directly without ad hoc assumptions [9] .By an application of the Betti-Rayleigh reciprocal theorem, Gregory and Wan developed a decay analysis technique determining the interior solution successfully and effectively. They provided the results for several plate problems, and derived a set of correct boundary conditions for arbitrarily prescribed admissible edgedata [10][11][12][13][14][15][16][17] . From these results, they have now explicit examples showing that the higher order accuracy offered by the governing differential equations of a higher order plate theory may not be attained unless commensurate boundary conditions are developed and used for these equations. These general results also show that, to be strictly correct, Saint-Venant's principle should generally be applied only to the leading term outer solution, i.e. the classical plate theory.Recently, relevant boundary conditions for elastic beams and piezoelectric beams have been attempted [18,19] . Moreover, Xu et al. [20] extended the model and method suggested by Gregory and Wan [11] for elastic plates to piezoelectric plates, which enables us to formulate the correct edge conditions for two-dimensional piezoelectric plate theories with the stress data. When str...