Crystal Growth from Silica Gels and Single Crystal Structure of Bariumchromate

Abstract

Rhonibic single crystals of bariumchroniate were grown in silica gels up t o 1.5 nim in size. The influence of the initial pH-value of the gel and the kind and concentration of reactants are studied. The crystal structure has been determined.

High-pressure transition to the post-barite phase in BaCrO4hashemite

“…As can be seen in Table I, the calculated lattice parameters and fractional coordinates compare very well to those from our experiment and previous reported data 36,37 , the unit-cell volume being only slightly underestimated (<1%). In Figure 5, it can be clearly seen that the theoretical energy-volume curves of the initial barite-type and the HP P2 1 2 1 2 1 post-barite-type phases cross each other at high pressure.…”

Preparation and structure characterization of nanocrystalline BaFeO4

“…2. Before indexing the peaks, we made an analysis on the possible structure of 4 , which have been studied in detail [16,19,20]. This inference accorded with previous reports which pointed out the isomorphism of BaFeO 4 with BaSO 4 and BaCrO 4 by comparing their X-ray powder diffraction patterns [21].…”

“…It is known that the bond length of [Cr-O](0.166 nm) in BaCrO 4 is between that of [S-O] (0.149 nm) in BaSO 4 and that of [U-O] in BaUO 4 (0.189 nm), and all of the three barium salts have similar structure[16][17][18][19]. Taking into account that theARTICLE IN PRESS…”

Notizen: Die Kristallstruktur von Calciumchromat(VI), CaCrO4 / The Crystal Structure of Calcium Chromate (VI), CaCrO4

“…E in K ristall d e r G rö ß e 80 x 40 x 20 w u rd e rö n tg e n o g ra p h isc h u n te rsu c h t. S chw enk-u n d W e isse n b e rg -A u fn a h m e n e rg a b e n ein te tra g o n a le s K ristallsy ste m , d ie R e fle x b e d in g u n g e n h k l : D ie D a te n s a m m lu n g e rfo lg te an ein em E n ra f-N o n iu s C A D -4 -D iffra k to m e te r (M o K a -S tra h lu n g ; G ra p h itm o n o c h ro m a to r im ein fa lle n d e n S tra h l). K rista llo g ra p h isc h e D a te n sow ie E in z e lh e ite n zu r [4] ). A lle rd in g s ist b ish e r n u r die K rista ll s tr u k tu r v o n B a C r 0 4 d u rc h ein e E in k rista ll-S tru ktu rv e rfe in e ru n g b eleg t [4], D ie S tru k tu rty p z u o rdn u n g e n fü r M g C r 0 4, C a C r 0 4 u n d S r C r 0 4 b e r u h e n im w e se n tlic h e n a u f P u lv e rd a te n .…”

“…K rista llo g ra p h isc h e D a te n sow ie E in z e lh e ite n zu r [4] ). A lle rd in g s ist b ish e r n u r die K rista ll s tr u k tu r v o n B a C r 0 4 d u rc h ein e E in k rista ll-S tru ktu rv e rfe in e ru n g b eleg t [4], D ie S tru k tu rty p z u o rdn u n g e n fü r M g C r 0 4, C a C r 0 4 u n d S r C r 0 4 b e r u h e n im w e se n tlic h e n a u f P u lv e rd a te n . L ediglich fü r C a C r 0 4 liegt ein e E in k rista llu n te rsu c h u n g aus d e m J a h re 1932 vo r [2].…”