Microwave Dielectric Properties of Lanthanide Titanate Ceramics

Abstract

Microwave dielectric property changes with substitution of La 3+ by Nd 3+ and/or Sm 3+ ions are studied for La 2 Ti 2 O 7 and La 4 Ti 9 O 24 ceramics. For the monoclinic La 2 Ti 2 O 7 , the substitution causes a considerable decrease in the permittivity (ε r ) of the material from ε r =47 (La) to ε r =36 (Nd), with a simultaneous variation in the Q · f value from 8500 to 16000 GHz. In La 4 Ti 9 O 24 -type dielectrics, only a slight change is observed in both the ε r (≈37) and Q · f values (≈24000 GHz) by lanthanide substitution. The effects of mixing of different dielectric materials on the microwave properties are also examined for La 2 Ti 2 O 7 -La 4 Ti 9 O 24 and Nd 2 Ti 2 O 7 -Nd 4 Ti 9 O 24 composites. The permittivity and temperature coefficient of resonant frequency of the composite ceramics can be controlled using Lichteneker's rule, whereas the mixing of the different dielectrics results in the substantial lowering of the Q · f value.