A factorial design approach for pressureless sintering in air of (Pb,La)(Zr,Ti)O3 synthesized via coprecipitation of oxide–alkoxides

Using factorial design for guidance, (Pb,La)(Zr,Ti)O3 (PLZT) ceramics of compositions 9.5/65/35 and 5/Z/T (Z/T = 60/40, 54/46, 40/60) were pressureless sintered in air. Theoretical bulk densities of up to 96% were achieved. The starting materials were obtained from the coprecipitation of the oxide–alkoxides. The relevant sintering parameters were initially screened with the 9.5/65/35 composition using a factorial design method to achieve high-density, high purity perovskite-phase, and small grain-size. The variables were ball-milling time, cold-press pressure, sintering time, sintering temperature, vacuum treatment, and PLZT to PbZrO3 weight ratio. The optimized sintering conditions were then applied to the remaining PLZT compositions, as well as to a commercially purchased PLZT powder, PLZT 8/40/60 to yield similar ceramic qualities. The ceramic samples were characterized with SEM, XRD, and Raman spectroscopy, and their relative permittivity, ɛr, and the piezoelectric constant, d33, were measured.