Tridymite

About: Tridymite is a research topic. Over the lifetime, 840 publications have been published within this topic receiving 14831 citations.

Wachstum und Verzwillingung von Tridymit

Abstract: Tridymit verzwillingt nach (3034) und (1016). Die ungewohnlichen Indizes der Zwillingsebenen lassen sich darauf zuruckfuhren, das Tridymitkristalle aus Cristobalitkeimen orientiert herauswachsen, und das sich die Zwillinge schon bei diesem paramorphen Ubergang von Cristobalit in Tridymit bilden. Auf diese Weise last sich das (3034)-Gesetz erklaren. Das (1016)-Gesetz findet seine Erklarung im Wachstum von Tridymitkristallen aus nach (111) verzwillingten Cristobalitkeimen. Im Rontgeneinkristalldiagramm zeigt sich die Verzwillingung auch bei makroskopisch ideal gewachsenen Kristallen. Durch polysynthetische Zwillingsbildung wird zwar nicht der Anteil, wohl aber die Verteilung der Si2O7-Gruppen mit ungunstiger Sauerstoffanordnung in der Tridymitstruktur geandert. The twin laws of tridymite are (3034) and (1016). These very highly indexed twin planes are unusually. Growth of tridymite starts from nuclei of cristobalite, and twinning results from the paramorphic transition of cristobalite into tridymite. This explaines the (3034)-law. If the cristobalite nuclei themselves are twinned according to the (111)-law, the tridymite growth results in (1016)-twins. The X-ray pattern of ideally grown single crystals of tridymite shows reflections due to polysynthetic twinning. This twinning makes a better distribution of Si2O7-groups with unfavourable oxygen arrangement in the structure.

Ceramic for enameling metallic material

Abstract: PURPOSE:To prevent the peeling of enameled ceramic from the base metal, by adding cristobalite and/or tridymite to a ceramic having a specific thermal expansion coefficient, thereby bringing the thermal expansion coefficient of the ceramic closer to that of the metal base. CONSTITUTION:In the preparation of ceramic for enameling the base metal of a dental crown or an ornament, the peeling of the ceramic from the metal after enameling the metal with the ceramic can be prevented bybringing the thermal expansion coefficient of the ceramic closer to that of the metal. This can be achieved by adding 1-60% cristobalite and/or tridymite to a ceramic containing e.g. 70-75% SiO2, 0.3-3.1% Al2O3, 4.6-9.6% CaO, 0.3-4.3% MgO, and 15- 17% Na2O and /or K2O and having a thermal expansion coefficient of >=85X 10 , crushing the mixture, kneading with water, shaping in the form of a rod, etc., bakig at 800 deg.C, and using the product as a raw material of the objective ceramic.

Simulation of oxygen vacancies at the Si-SiO2 interface

Abstract: The Si(001)/SiO2 (tridymite) interface has been simulated using a Monte-Carlo method It has been shown that in this way reasonable values of angles and interatomic distances are obtained The oxygen defect formation energy dependence with different vacancy sites has been studied Because of coulombic interactions, the formation of vacancies is much easier in the vicinity of the interface

Liminous oxide having stuffed tridymite type or kaliphilite type structure and oxide luminophor

Abstract: PROBLEM TO BE SOLVED: To obtain a luminous oxide which shows excellent heat resistance and chemical stability, is useful for a luminophor of a high luminance capable of emitting light of colors from blue to yellow and shows afterglow by using a compound oxide having a specific composition SOLUTION: An oxide to be used has a stuffed tridymite type structure having a composition of M1M22O4 or a kaliphilite type structure having a composition of M1M32O4 (wherein M1 is an alkaline earth metal element selected from Ca, Sr and Ba; M2 is a metal element selected from Al and Ga; and M3 is Si, Mg or Zn) Further, the alkaline earth metal element M1 of the oxide is substituted by a divalent ion of europium or a trivalent ion of other rare earth metal element provided that the substitution ratio is not more than 30 mol% of the sum of the alkaline earth metal element ions