INSTITUTE OF PHYSICS PUBLISHING JOURNAL OF PHYSICS D: APPLIED PHYSICS J. Phys. D: Appl. Phys. 37 (2004) 1980–1986 PII: S0022-3727(04)78506-X Relationship between microwave and lattice vibration properties in Ba(Zn 1/3 Nb 2/3 )O 3 -based microwave dielectric ceramics Stanislav Kamba 1 , Hana Hughes 2 , Dmitri Noujni 1 , Santhi Surendran 1 , Robert C Pullar 3 , Polina Samoukhina 1 , Jan Petzelt 1 , Robert Freer 2 , Neil McN Alford 3 and David M Iddles 4 1 Institute of Physics, Academy of Science of the Czech Republic, Na Slovance 2, 182 21 Praha 8, Czech Republic 2 Manchester Material Science Centre, University of Manchester and UMIST, UK 3 Centre for Physical Electronics and Materials, London South Bank University, London SE1 0AA, UK 4 Filtronic Comtek, Ceramics Division, Enterprise Drive, Station Road, Four Ashes, Wolverhampton WV10 7DB, UK Received 30 March 2004 Published 30 June 2004 Online at stacks.iop.org/JPhysD/37/1980 doi:10.1088/0022-3727/37/14/014 Abstract The dielectric properties of (1 − x)Ba(Zn 1/3 Nb 2/3 )O 3 –x Ba (Ga 1/2 Ta 1/2 )O 3 (BZN–x BGT) microwave (MW) ceramics, with x between 0 and 0.2, and those of 0.9Ba(Zn 0.6 Co 0.4 ) 1/3 Nb 2/3 O 3 –0.1Ba(Ga 0.5 Ta 0.5 )O 3 (BZCN–BGT) were studied at MW, terahertz (THz) and infrared (IR) frequencies at temperatures from 10 to 300 K. At room temperature, the temperature coefficient of resonance frequency (τ f ) near 3 GHz decreases from 28 ppm K −1 in undoped BZN to 2 ppm K −1 in BZN–0.2BGT and reduces to zero in BZCN–BGT. The addition of BGT to BZN depresses the dielectric Q value, but incorporation of Co improves the Q values, yielding Q ∼ 30 000 at 3 GHZ in BZCN–BGT. The relative permittivity (ε ′ ) exhibits only limited variation with composition (ε ′ values in the range 34.4–36.0). IR and THz spectra as well as the low-temperature MW dielectric measurements revealed a weak dielectric relaxation below phonon frequencies, possibly arising from charges caused by inhomogeneous distribution of the B-site ions with differing valences. The IR reflectivity spectrum of BZN–0.2BGT is significantly different (smeared) compared with other compositions, which may be caused by disorder on the B sites and by an amorphous phase at the grain boundaries. 1. Introduction Wireless telecommunication techniques have witnessed rapid development in the last decade in response to the expansion of mobile telephone systems and satellite communication. Modern communication systems have moved to the microwave (MW) frequency region, where advanced dielectric ceramics are frequently used in resonators and filters. Miniaturization requires high relative permittivity (ε ′ ) materials (since the size of resonators is inversely proportional to √ ε ′ ) with a small or zero temperature coefficient of resonance frequency τ f (|τ f | < 10 ppm K −1 ). Furthermore, ceramics with low dielectric loss, ε ′′ (often described in terms of high dielectric quality, Q = ε ′ /ε ′′ ) are needed for the high selectivity and optimized bandwidth of the filters [1]. 0022-3727/04/141980+07$30.00 © 2004 IOP Publishing Ltd Printed in the UK 1980