STRUCTURAL TRANSITIONS IN PB(ZR,TI,W,CD)O-3 FERROELECTRIC-FILMS

Pb(Zr,Ti,W,Cd)O-3 ferroelectric films, epitaxial on (001) MgO cleaved surfaces and polycrystalline on Pt and Al2O3 substrates, were grown by rf cathode sputtering of stoichiometric ceramic targets in an oxygen atmosphere (100-180 Pa). According to x-ray diffraction studies, the e pitaxial films have a tetragonal structure at room temperature and und ergo a transition to a cubic phase at similar or equal to 370 degrees C. The transition is accompanied by a minimum in lattice parameter, ch anges in the width of diffraction peaks, and a decrease in the integra ted intensity of reflections with h + k + I = 2n + 1. The polycrystall ine films have a pseudocubic structure at room temperature. Their latt ice parameter varies monotonically with temperature; the only evidence for the transition from the noncentrosymmetric, ferroelectric phase t o the centrosymmetric, cubic phase is the decrease in the integrated i ntensity of reflections with h + k + l = 2n + 1.