The dielectric constants and dissipation factors of LiA1Si206, CaAI2SizO8 and CaMgSi206 in both the crystalline (e-spodumene, anorthite, and diopside) and amorphous forms were determined at I MHz using a two-terminal method and empirically determined edge corrections. The results are: spodumene tc'11 = 7.30 tan 6=0.0007 KTt22 = 8.463 tan 6 = 0.0002 ~:'33 = 11.12 tan 6=0.0007 anorthite ~c'a. = 5.47 tan 6 = 0.0009 ~:'b* = 8.76 tan 6=0.0010 ~'o. = 7.19 tan 6=0.0013 diopside ~:'11 = 9.69 tan 6=0.0016 โข'22 = 7.31 tan 6=0.0007 X'as = 7.29 tan 6=0.00019 LiA1SizO6 to' = 8.07 tan ~--0.047 amorphous CaA12SizO8 ~c' = 7.50 tan 6=0.0024 amorphous CaMgSi206 to' = 8.89 tan 6=0.0021 amorphous
The dielectric properties of a spodumene glass, progressively crystallized at different conditions, were also determined. As the crystallization temperature was increased from 720 to 920 ~ C, ~' increased from 6.22 to 6.44. The dissipation factor, tan 6, remained constant at 0.020. Similarly, as the crystallization time at 750 ~ C increased from 0.5 hr to 6.0 hr, ~:' increased from 6.28 to 6.35. The deviations of the measured dielectric polarizabilities as determined from the Clausius-Mosotti equation from those calculated from the sum of oxide polarizabilities according to eD(mineral, glass)= S eD(Oxides) are +7.4% for ~-spodumene, +1.2% for diopside, and +28.0, + 19.6 and + 15.9% for amorphous spodumene, anorthitie and diopside compositions, respectively. Positive deviations in e-spodumene and anorthite are consistent with lower than normal apparent cation bond valence sums and are believed to be evidence for loosely bonded ~ rattling" Li and Ca ions. Diopside, with Ca and Mg ions having normal bond valence sums, exhibits no abnormal deviation from additivity. Larger positive deviations in amorphous SiO2, LiA1Si206, CaAlzSizOs and CaMgSi:O6 are postulated to arise from a combination of loosely bonded cations and disordered O = ions where the oxygen dielectric polarizability increased from its normal value of 2.0 ~3 in well-behaved oxides to 2.2-3.0 A s in the amorphous phases.