3D Residual Strain in DKDP Crystals by Neutron Diffraction

Neutron diffraction technique is applied to study the three-dimensional (3D) residual strains in K(H_{1− x}D_x)₂PO₄ (DKDP) crystals with various deuterium contents (0 ≤ x ≤ 0.99). It is found that the residual strains in the crystalline coordinate are at the magnitude of 10⁻³ to 10⁻⁴. The results show that the level of the macro-strain in the crystal bulk is independent of the deuteration level. However, when the deuteration level is below 50%, the average of micro-strain increases first with the increasing of deuteration level, then decreases when the deuteration level is in excess of 50%. According to the residual strains, the internal stresses are calculated through σ_ij = C_ijklε_kl. Finally, the potential sources of the stresses in crystals are discussed and analyzed.