Types of Quartz Under normal pressure
the quartz crystal has five different properties with the temperature difference, namely:
(1) α-quartz, its temperature is below 573 ℃ when the steady state, we usually use the piezoelectric Quartz crystals belong to this category.
(2) β quartz, α quartz heating over 573 ℃, that is converted to β quartz, it is 573 ℃ ~ 870 ℃ between the steady state, but this time there is no piezoelectric effect, can not be used as piezoelectric element Device.
(3) phosphorus quartz, when the β-quartz heating more than 870 ℃, β quartz into phosphorus quartz, it is between 870 ℃ ~ 1470 ℃ steady state.
(4) square quartz, when the phosphorus quartz heating more than 1470 ℃, the phosphorus quartz into square quartz, it is between 1470 ℃ ~ 1710 ℃ steady state.
(5) quartz glass, when the other side of the quartz heating more than 1710 ℃ and after the beginning of melting, melting quartz, the temperature can not be restored to the above form. It can be seen, we commonly used α quartz, the critical temperature of 573 ℃. If it exceeds this temperature, it will lose the piezoelectric effect, which is our process must pay great attention to the problem. Under special conditions, there are two variants of quartz and quartz.
(6) Ke Shiying is a high-pressure phase polytype of quartz that changes into a metastable state under the action of shock wave. The density is 3.01g / cm3. In the mirror for the very fine, high refractive index of the particles, about 200 ~ 1100μm size, embedded in the modified quartz glass. Single crystal is very small (~ 1μm), was tetrahedral structure. The aggregates are arranged in a plane parallel to the different directions, and the refractive index is extremely low. Some aggregates are colorless, brown or nearly opaque. In the high temperature state of instability, easy to change into a scale quartz or square quartz.
(7) Sri Lanka is quartz is more dense high-pressure phase polytype, the density of 4.35g / cm3, by the common side octahedral chain composition, with rutile structure. In 1961, a former Soviet scientist named Stischauvov found that if the silica was in an ultrahigh pressure state, its atoms were very close and became extremely dense. A cubic inch of flattened sand is much heavier than a cubic inch of ordinary sand. This flattened sand is therefore called "stone." Ordinary sand in the state of ultra-high pressure into a dense "Sri Lanka", "Sri Lanka" in the natural state of millions of years of experience, will return to the sand. In the laboratory, with the high temperature of 850 degrees Celsius "stone quartz" heating for 30 minutes, will become ordinary sand.