Sintering Behavior and Electrical Properties of Nanosized Doped-ZnO Powders Produced by Metallorganic Polymeric Processing

Homogeneous and nanosized (28 nm crystallite size) doped-ZnO ceramic powders were obtained by a metallorganic polymeric method. Calcining and granulating resulted in green compacts with uniform powder packing and a narrow pore-size distribution (pore size 19 nm). Dense ceramic bodies (>99% of theoretical) were fabricated by normal liquid-phase sintering at 850° and 940°C for 1–5 h. Apparently, the low pore-coordination number allowed a uniform filling of the small pores by the liquid formed in the early stages of sintering, and, consequently, high shrinkage and rapid densification occurred in a short temperature interval (825°–850°C). At these sintering temperatures, limited grain growth occurred, and the grain size was maintained at <1 μm. Ceramics so-fabricated showed a nonlinear coefficient, α, of ≥70, and a breakdown voltage, V _b (1 mA/cm²), of ≥1500 V/mm. The high electrical performance of the doped-ZnO dense ceramics was attributed to liquid-phase recession on cooling, which enhanced the ZnO-ZnO direct contacts and the potential barrier effect.