TY - JOUR
T1 - Crystal Structure and Microwave Dielectric Properties of LiRE9(SiO4)6O2 Ceramics (RE = La, Pr, Nd, Sm, Eu, Gd, and Er)
AU - Manu, Kurusaroor Mana
AU - Karthik, Chinnathambi
AU - Leu, Lii-Cherng
AU - Lazar, Kokken Anlin
AU - Ubic, Rick
AU - Sebastian, Mailadil T.
AU - Chinnathambi, Karthik
PY - 2013/5
Y1 - 2013/5
N2 - The crystal structure and microwave dielectric properties of apatite-type LiRE9(SiO4)6O2 ceramics (RE = La, Pr, Nd, Sm, Eu, Gd, and Er) have been investigated. The densification of lithium apatites has been greatly improved with the addition of 1 wt% LiF. Selected area electron diffraction and X-ray diffraction (XRD) Rietveld analysis confirm that these compounds belong to the P63/m (No. 176) space group with hexagonal crystal symmetry. The porosity-corrected relative permittivity was found to decrease with decreasing ionic polarizability of RE3+ ions. Relationships between the structural parameters and microwave dielectric properties have been examined. The observed variation in the quality factor of LiRE9(SiO4)6O2 + 1 wt% LiF ceramics (RE = La, Pr, and Nd) was correlated with average cation covalency (%). The temperature coefficient of resonant frequency was found to depend on the bond valence sum of cations. LiEr9(SiO4)6O 2 + 1 wt% LiF ceramics showed good microwave dielectric properties with εr = 12.8, Qu × f = 13000 GHz and τf = +17 ppm/°C. All the compositions showed low coefficient of thermal expansion with thermal conductivity in the range 1.3-2.8 W (m K) -1.
AB - The crystal structure and microwave dielectric properties of apatite-type LiRE9(SiO4)6O2 ceramics (RE = La, Pr, Nd, Sm, Eu, Gd, and Er) have been investigated. The densification of lithium apatites has been greatly improved with the addition of 1 wt% LiF. Selected area electron diffraction and X-ray diffraction (XRD) Rietveld analysis confirm that these compounds belong to the P63/m (No. 176) space group with hexagonal crystal symmetry. The porosity-corrected relative permittivity was found to decrease with decreasing ionic polarizability of RE3+ ions. Relationships between the structural parameters and microwave dielectric properties have been examined. The observed variation in the quality factor of LiRE9(SiO4)6O2 + 1 wt% LiF ceramics (RE = La, Pr, and Nd) was correlated with average cation covalency (%). The temperature coefficient of resonant frequency was found to depend on the bond valence sum of cations. LiEr9(SiO4)6O 2 + 1 wt% LiF ceramics showed good microwave dielectric properties with εr = 12.8, Qu × f = 13000 GHz and τf = +17 ppm/°C. All the compositions showed low coefficient of thermal expansion with thermal conductivity in the range 1.3-2.8 W (m K) -1.
UR - https://scholarworks.boisestate.edu/mse_facpubs/158
UR - https://doi.org/10.1111/jace.12215
U2 - 10.1111/jace.12215
DO - 10.1111/jace.12215
M3 - Article
SN - 0002-7820
VL - 96
SP - 1504
EP - 1511
JO - Journal of the American Ceramic Society
JF - Journal of the American Ceramic Society
IS - 5
ER -