Bond angle study of self-compensating Y _1-xCa _xBa _2-xLa _xCu ₃O _z system

Single-phase samples of a self-compensating Y _1-xCa _xBa _2-xLa _xCu ₃O _z system were synthesized through a solid-state reaction method with x < 0.4. The structure of all samples were characterized by X-ray diffraction and refined by the Rietveld method. Superconducting properties have been investigated by the DC magnetization measurement. The critical temperature (T _c) decreases evidently with the increment of x although the carrier concentration remains constant in the samples for different doping level. Careful study of the chemical bonds in the crystalline lattice demonstrates that the T _c is closely correlated to four pairs of bond angles in the unit cell. The analysis indicates that crystalline structure is one of the important factors to high-T _c superconductivity, and its influence is independent of the carrier concentration.