Crystallization Pathways of Cerium(IV) Phosphates Under Hydrothermal Conditions: A Search for New Phases with a Tunnel Structure

Abstract

Hydrothermal crystallization pathways of amorphous ceric phosphate gels were found to be determined by the ammonia concentration in a reaction medium. This allows for highly selective hydrothermal synthesis of various finely crystal-

Amorphous and crystalline cerium(iv) phosphates: biocompatible ROS-scavenging sunscreens

“…According to the results of X-ray diffraction, the crystalline cerium(IV) phosphates obtained were single-phase; their diffraction patterns were identical to those of Ce(PO 4 )(HPO 4 ) 0.5 (H 2 O) 0.5 and NH 4 Ce 2 (PO 4 ) 3 presented elsewhere. 67,69 The diffraction pattern of the amorphous cerium(IV) phosphate also corresponded to previously reported data 67 (see Fig. 1).…”

On the Thermal Decomposition of Cerium(IV) Hydrogen Phosphate Ce(PO4)(HPO4)0.5(H2O)0.5

“…The IR spectrum of initial compound fully corresponds to literature data [11,25,26]. All IR spectra presented in Fig.…”

“…Let us note that the retention of structural motif and inheritance of microstructure during thermolysis was noted also for other cerium(IV) phosphates [11,15]. The structures of tetravalent cerium phosphates seems to be rather stable on heating to 500-600°С and do not degrade on water removal.…”

“…Tetravalent cerium seems to form no normal phosphates [6,7] (let us note that Mašín and Doležal [8] proposed procedure for gravimetric determination of cerium(IV) content in solutions by its precipitation as a normal phosphate). Examples are known for reliably characterized crystalline double and mixed cerium(IV) phosphates (NH 4 ) 2 Ce(PO 4 ) 2 •H 2 O [9], K 2 Ce(PO 4 ) 2 [10], NH 4 Ce 2 (PO 4 ) 3 [11], Na 10 Ce 2 P 6 O 24 [12], K 4 CeZr(PO 4 ) 4 [13], (NH 4 )[CeF 2 (PO 4 )] [14], CeOHPO 4 , and Ce 2 O(PO 4 ) 2 [15]. Cerium(IV) hydrogen phosphates are apt to exist as gel-like amorphous compounds of variable compositions.…”

Meet the Cerium(IV) Phosphate Sisters: CeIV(OH)PO4 and CeIV2O(PO4)2

“…[1,47] The vibration frequency located at 795 cm À1 is supposed to be the stretching mode of the (Ce)-O-H. [46,47,49] Evidence that this band belongs specifically to the vibrations of the OH group and not to crystallization water is providedb yt he absence of as imilar band in the IR spectra of Ce(PO 4 )(HPO 4 ) 0.5 (H 2 O) 0.5 and (NH 4 ) 2 Ce(PO 4 ) 2 (H 2 O). [11,50] The region in the range 1200-440 cm À1 (except for the band at 795 cm À1 )i sc haracteristic of cerium phosphates and corresponds to vibrations of PÀObonds. [51,52] Thermal decomposition of Ce(OH)PO 4 proceeds in two clearly distinguishable stages:1 00-300 8Ca nd 600-700 8C (Figure 4).…”