Über Zirkonate, Hafnate und Thorate von Barium, Strontium, Lithium und Natrium

Abstract

Inhaltsiibersicht I n den Systemen MIIO/XIVO, (MI1 = Sr, Ba; XIv = Zr, Hf) existieren neben den Metaverbindungen basenreichere Verbindungen des Typs M:IXIVO, mit tetragonaler K,NiF,-Struktur. Eingehende Untersuchungen in den Systemen Li,O/X1vO, (XIV = Zr, Hf) fiihrten zur Darstellung und Charakterisierung der neuen Verbindungstypen Li4XIv0, und L&XIVO,. Tho, bildet mit Erdalkali-und Alkalioxiden nur Metaverbindungen, tritt jedoch mit Li,O uberhaupt nicht in Reaktion. Zwischen Na,ThO, und Li,ZrO, besteht nach den Rontgenpulverdiagrammen eine enge strukturelle Beziehung. SummaryIn the systems MIIO-XIVO, with MI1 = Sr, Ba; XIv = Zr, Hf besides meta compounds more basic compounds of the typeM:IXIV04, having the tetragonal K,NiF, structure, exist. Investigations on the systems Li,O-XxIVO, (XI"= Zr, Hf) resulted in the preparation and characterisation of the new compound types Li4XIV04 arid Li,XWO,.Tho, gives with alkaline-earth and alkali metal oxides only meta compounds, however. no reaction with Li,O. A close structural relation between Na,ThO, and Li,ZrO, exists according to their X-ray powder diagrams. EinleitungI m Rahmen der Untersuchungen uber zahlreiche Oxidsysteme durch SCHOLDER und Mitarbeiter 2, wurden auch die Systeme ZrO,/MTIO bzw. M i 0 (MI' = Ba, Sr; MI = Li, Na), HfO,/M1'O bzw. Mi0 (MI1 = Ba, Sr; MI = Li) und ThO,/M"O bzw. M i 0 (MI' = Ba; MI = Na) eingehend mit dem besonderen Ziel der Darstellung und Charakterisierung basenreicher Verbindungen bearbeitet .

Crystal Structure and Microwave Dielectric Properties of Alkaline‐Earth Hafnates, AHfO3 (A=Ba, Sr, Ca)

“…It is generally accepted that the room‐temperature crystal structure of BaHfO 3 can be described by a cubic unit cell; however, there are discrepancies concerning the unit cell length. For example, Scholder et al 27 reported a =4.171 Å, whereas Gooden and McCarthy 28 reported a =8.333 Å. The exact crystal structure of SrHfO 3 has also been a matter of some controversy.…”

Synthesis of BaZr0.75Hf0.25O3 by a solid-state reaction technique and characterizations of dielectric properties

“…The partial substitution of Sr by Ba, namely Sr x Ba 1−x HfO 3 , produces a series of new compounds where there is a competition between Sr-O and Ba-O bonds due to the different ionic radius and valence electrons. At minor temperature, a lower symmetry structure in the shape of a distorted cubic arrangement can be found [7][8][9]. Kennedy et al [10] also described the symmetry of Sr 0.5 Ba 0.5 ZrO 3 at room temperature as orthorhombic in Imma, and noted that only a small increase in the Ba content was sufficient to induce a transition to the tetragonal structure.…”

Subsolidus phase relations of the SrO–MO2–CuO systems (M=Ti, Zr and Hf) at 900°C in air

“…At temperatures in excess of 1400 • C, the existence of four binary oxide phases was reported: SrZrO 3 , Sr 4 Zr 3 O 10 , Sr 3 Zr 2 O 7 and Sr 2 ZrO 4 [18][19][20][21][22]. According to calculated phase diagram sections [23,24], the Sr 4 Zr 3 O 10 , Sr 3 Zr 2 O 7 and Sr 2 ZrO 4 phases are expected to be stable down to at least 725 • C. However, the experimental study of Tilloca and Perez y Jorba [22] demonstrates that only the SrZrO 3 phase is stable at 900 • C in air.…”

“…The SrO-TiO 2 system was studied by Drys and Trzebiatowsi [16] as well as by Cocco and Massazza [17] although at temperatures in excess of 1200 • C. Similarly, several authors have studied the SrO-ZrO 2 system, but mostly at temperatures higher than 1400 • C [18][19][20][21], with the exception of Tilloca and Perez y Jorba [22], who extended their investigations down to 1000 • C. For this system, calculated phase equilibria are also available [23,24]. The SrO-HfO 2 system was studied in details by Shevchenko et al [25] and by Delamarre [26] at temperatures higher than 1600 and 1250 • C, respectively.…”