New Transitory Form of Silica
June 23, 2015 | Carnegie ScienceEstimated reading time: 2 minutes
A Carnegie-led team was able to discover five new forms of silica under extreme pressures at room temperature.
Silicon dioxide, commonly called silica, is one of the most-abundant natural compounds and a major component of the Earth’s crust and mantle. It is well-known even to non-scientists in its quartz crystalline form, which is a major component of sand in many places. It is used in the manufacture of microchips, cement, glass, and even some toothpaste.
Silica’s various high-pressure forms make it an often-used study subject for scientists interested in the transition between different chemical phases under extreme conditions, such as those mimicking the deep Earth.
The first-discovered high-pressure, high-temperature denser form, or phase, of silica is called coesite, which, like quartz, consists of building blocks of silicon atoms surrounded by four oxygen atoms. Under greater pressures and temperatures, it transforms into an even denser form called stishovite, with silicon atoms surrounded by six oxygen atoms. The transition between these phases was crucial for learning about the pressure gradient of the deep Earth and the four-to-six configuration shift has been of great interest to geoscientists. Experiments have revealed even higher-pressure phases of silica beyond these two, sometimes called post-stishovite.
A chemical phase is a distinctive and uniform configuration of the molecules that make up a substance. Changes in external conditions, such as temperature and pressure, can induce a transition from one phase to another, not unlike water freezing into ice or boiling into steam.
The team, including Carnegie’s Qingyang Hu, Jinfu Shu, Yue Meng, Wenge Yang, and Ho-Kwang, “Dave” Mao, demonstrated that under a range from 257,000 to 523,000 times normal atmospheric pressure (26 to 53 gigapascals), a single crystal of coesite transforms into four new, co-existing crystalline phases before finally recombining into a single phase that is denser than stishovite, sometimes called post-stishovite, which is the team’s fifth newly discovered phase. This transition takes place at room temperature, rather than the extreme temperatures found deep in the earth.
Scientists previously thought that this intermediate was amorphous, meaning that it lacked the long-range order of a crystalline structure. This new study uses superior x-ray analytical probes to show otherwise—they are four, distinct, well-crystalized phases of silica without amorphization. Advanced theoretical calculations performed by the team provided detailed explanations of the transition paths from coesite to the four crystalline phases to post-stishovite.
“Scientists have long debated whether a phase exists between the four- and six-oxygen phases,” Mao said. “These newly discovered four transition phases and the new phase of post-stishovite we discovered show the missing link for which we’ve been searching.”
The paper’s other co-authors are Adam Cadien of George Mason University and Howard Sheng of both the Center for High Pressure Science and Technology Advanced Research in Shanghai, China, and George Mason University.
Suggested Items
Kerafol, X2F Partner to Revolutionize Thermal Solutions for Electronic Devices
02/09/2024 | KerafolKerafol and X2F are teaming up to develop state-of-the-art thermal management solutions for electronic devices by leveraging the advantages of Kerafol's thermally conductive materials and X2F's patented controlled-viscosity molding technologies.
Book Excerpt: 'The Printed Circuit Designer's Guide to... Manufacturing Driven Design,' Chapter 2
08/23/2023 | I-Connect007 Editorial TeamChapter 2 of 'The Printed Circuit Designer's Guide to... Manufacturing Driven Design' explores why a change is needed due to increasing complexity in electronics design. The miniaturization and resultant increase in number of design features make it virtually impossible to manually verify a design's manufacturing fit.
TT Electronics Roxspur Product Line Takes New Strategic Approach to Marketing DPG Series
08/15/2023 | TT ElectronicsTT Electronics, a global provider of engineered technologies for performance-critical applications, breaks new ground with its Roxspur Measurement and Control product line’s first order of the Digital Pressure Gauge (DPG) series placed by global electronics distributor DigiKey.
Designing Aerospace PCBs: A Galaxy of Challenges
07/11/2023 | I-Connect007 Editorial TeamJeffrey Boye designs aerospace PCBs at the Johns Hopkins University Applied Physics Laboratory. After a decade or so at the APL, some of his boards are currently floating in space. Jeffrey recently took a class with IPC instructor Kris Moyer titled “PCB Design for Military and Aerospace Applications.” As Jeffrey explains in this interview, this exhaustive class covered everything from high-reliability DFM techniques to Paschen’s curves, which help engineers understand and predict how a high-voltage signal travels in different atmospheres. He also discusses some of the “wacky” projects that he’s worked on at the APL, and the need to communicate with fabricators early on with aerospace applications.
Global Demand for Notebooks Projected to Grow 11% QoQ in 2Q23
04/06/2023 | TrendForceTrendForce research reveals that global notebook shipments reached 33.9 million units in 1Q23—a 13% QoQ and 39% YoY decline. This drop is primarily attributed to the continued impact of economic headwinds on consumer market confidence, which has hindered notebook channels as they destock.