Variations in the Ferroelectric and Piezoelectric Properties of Lead Zirconate Titanate Ceramics Containing Cr sub 2 O sub 3Additions.

摘要

Effects of Cr sub 2 O sub 3additions to Pb(Zr sub 0 . sub 52 ,Ti sub 0 . sub 48 ) O sub 3 (PZT) were investigated by doping with 0.05and 0.20wt. percent Cr sub 2 O sub 3and measuring dielectric,ferroelectric,and piezoelectric properties before and after poling under different conditions for time and temperature. The effects of Cr sub 2 O sub 3were also studied by recording the current in a poling circuit as a function of an applied dc field increasing at a constant rate. The piezoelectric planar coupling coefficient, k/sub p/,was found to be increased at the low doping level,and decreased slightly at the higher doping level relative to the unmodified PZT. The addition of Cr sub 2 O sub 3was found to have the reverse effects on the mechanical quality factor, Q/sub M/. The variation of piezoelectric properties resulting from the addition of Cr sub 2 O sub 3is postulated to be due to the solution of chromium in PZT primarily as Cr exp +6 , a lead vacancy generator,at the low doping level,and as Cr exp +3 ,an oxygen vacancy generator,at the higher doping level. Dielectric and ferroelectric properties of the modified PZT relative to the unmodified PZT supported this. Polarization-field hysteresis indicated a domain wall pinning mechanism was operative in the modified PZT and is concluded to be a result of an increased vacancy concentration along domain walls. Increased poling time or temperature resulted in higher values of k/sub p/and significant changes in dielectric and ferroelectric properties of each composition studied. The poling time and temperature dependence of electrical properties is believed to be due to the rate of diffusion of vacancies,and domain wall mobility,both increasing as the temperature is raised and resulting in higher saturation and remnant polarizations. The current-field relationships measured during poling at 25and 100exp 0 C and polarization reversal at 25exp 0 C supported this supposition. (ERA citation 01:013705)