ZnAl2O4 and (0.79)ZnAl2O4–(0.21)Mn2TiO4 Microwave Dielectric Ceramics Prepared by Hot Pressing and Spark Plasma Sintering

Abstract

Ceramics of ZnAl2O4 (ZA) and 0.79ZnAl2O4–0.21Mn2TiO4 (ZAMT) were prepared by the mixed oxide route using hot pressing and spark plasma sintering (SPS) techniques. Sintering temperatures were 1300°C in all cases; hot‐pressed samples were held at peak temperature for 1 h, the SPS samples for 5 min. Sintered densities were at least 98% theoretical for the SPS samples. ZnAl2O4 prepared by SPS was single phase; all other samples contained minor amounts of second phase. Grain sizes for ZnAl2O4 were typically 200–500 nm, but 2–5 μm for ZAMT. FTIR spectra for all the samples include Al–O bend mode band at ~450 cm−1. The microwave dielectric properties of the ZA‐SPS (εr = 8.7; Qxf = 57 000 GHz) were comparable with conventionally produced samples; the dielectric properties of the ZAMT‐SPS (εr = 9.6; Qxf = 30 630 GHz) were superior to conventionally produced ceramics. The SPS approach yielded high density, high quality dielectric ceramics at lower sintering temperatures and much reduced processing times.