Effect of isovalent substitutions on the microwave dielectric properties of Ca4La6(SiO4)4(PO4)2O2 apatite

Autor: Mailadil Thomas Sebastian, Pulanchiyodan Abhilash, Dhanesh Thomas
Rok vydání: 2013
Předmět:
Zdroj: Journal of Alloys and Compounds. 546:72-76
ISSN: 0925-8388
DOI: 10.1016/j.jallcom.2012.08.085
Popis: The isovalent substitutions of Sr2+, Pr3+, (GeO4)4− and (VO4)3− in the respective cationic and anionic sites of Ca4La6(SiO4)4(PO4)2O2 have been accomplished. The substitution of Sr2+ for Ca2+ decreases er and Qu × f but increases the τf. The value of er increases and Qu × f decreases when (GeO4)4− is substituted for (SiO4)4− with a marginal variation in τf. The gradual replacement of (PO4)3− with (VO4)3− brings about an increase in er and τf with a small decrease in Qu × f. The partial substitution of Pr3+ for La3+ is found to be effective in decreasing the τf without much affecting er and Qu × f. The composition Ca4(La4Pr2)(SiO4)4(PO4)2O2 shows good microwave dielectric properties: er = 13.8, Qu × f = 26000 GHz and τf = −7 ppm/°C. The ceramics have low linear coefficient of thermal expansion (4–5 ppm/°C).
Databáze: OpenAIRE