Geoscience Reference
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Table 5.4 Physical Properties of Berlinite and Quartz (Schwarzenbach, 1966) [69]
Properties
AlPO 4
Quartz
Density
2.64 (natural)
2.655
2.56 (artificial)
6 7
Hardness
7
n e
1.529 6 0.003
1.544
n o
1.519 6 0.003
1.535
Birefringence
0.01
0.009
1
1
a
4.94291
4.9138
c
10.94761
5.4052
5.4738 ˚
c/z
c/a
2.21481
1.10
c/2a
1.1074
Space group
P3 1 21 or P3 2 21
P3 1 21 or P3 2 21
z
3
3
Table 5.5 Tentative Comparison with Quartz (Thickness Y Rotated Resonators
at Same Frequency)
Enhanced by 1.4 1.5
Useful Coupling Coefficient (AT Filter Trapped
Resonators)
Shift of oscillators or bandwidth of filters (AT-cut)
Twice
Angular sensitivity (first-order FTC)
Reduced
Thermal stability (higher order FTC)
Better
Q factor propagation losses
Already sufficient (may be
comparable)
Thickness of plates (AT)
Reduced by 1.15
Electrode dimensions (AT)
Reduced by 1.32 (TT)
(Same plating 2D TT of TS)
Reduced by 1.23 (TS)
Nonlinear properties
To be determined
“Dry” berlinite has similar C, E, EPS constants, first-order TC and much reduced higher order TC.
Today it is possible to grow more than 500 kg of dislocation-free high-purity
quartz in a single experimental run. However, in the case of berlinite, it cannot be
more than a few hundred grams. The major problem is the highly corrosive phos-
phoric acid media in which the growth takes place.
5.3.1 Crystal Chemical Significance of the Growth of AlPO 4 Crystals
Berlinite is isostructural with quartz, Si(SiO) 4 , and the artificial compound AlAsO 4 .
It shows the same thermal inversion as SiO 2 [79] , although, at slightly lower
temperatures, it crystallizes in hexagonal system—trigonal trapezohedral class-32.
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