Ba 8 ZnTa 6 O 24 : a high-Q microwave dielectric from a potentially diverse homologous series

The ceramic ${\mathrm{Ba}}_8{\mathrm{ZnTa}}_6{\mathrm{O}}_{24}$ has been synthesized in isolation and its dielectric and crystallographic properties characterized. The material affords excellent dielectric properties, with a high unloaded quality factor $Q_u\text{=20\hspace{0.05em}800}$ at 3.28 GHz, high relative permittivity ${\epsilon }_r\text{=29}$ and a temperature coefficient of resonant frequency ${\tau }_f\text{=29.4\hspace{0.17em}}\mathrm{ppm}\mathrm{/°}\mathrm{C}.$ The crystal structure adopted is complex, comprising mixed cubic and hexagonal perovskite subunits, and contains cation vacancies on the octahedral sites. A second phase with a closely related structure is identified, demonstrating the existence of a family of materials. This structural complexity offers diverse opportunities for substitutions calculated to enhance the figures of merit reported.