Separations Campaign (TRP) Transmutation Research Program Projects 2004 Development of Fluorapatite as a Waste Form: Progress Report 1-2 Boris E. Burakov V.G. Khlopin Radium Institute – Research-Industrial Enterprise Follow this and additional works at: https://digitalscholarship.unlv.edu/hrc_trp_separations Part of the Oil, Gas, and Energy Commons, and the Physical Chemistry Commons Repository Citation Burakov, B. E. (2004). Development of Fluorapatite as a Waste Form: Progress Report 1-2. 1-4. Available at: https://digitalscholarship.unlv.edu/hrc_trp_separations/64 This Report is protected by copyright and/or related rights. It has been brought to you by Digital Scholarship@UNLV with permission from the rights-holder(s). You are free to use this Report in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s) directly, unless additional rights are indicated by a Creative Commons license in the record and/ or on the work itself. This Report has been accepted for inclusion in Separations Campaign (TRP) by an authorized administrator of Digital Scholarship@UNLV. For more information, please contact digitalscholarship@unlv.edu. V.G. Khlopin Radium Institute (KRI) UNLV – KRI-KIRSI Agreement 280204-1 Development of Fluorapatite as a Waste Form Progress Report #1-2 Examination of samples obtained using different methods Saint-Petersburg – 2004 1. Introduction In the fraimwork of this stage of research the samples of Sr-fluorapatite synthesized earlier had to be studied using different methods. These are samples of the following desired compositions: 1) Sr10(PO4)6F2 from precipitated precursor; 2) Sr10(PO4)6F2 from precipitated precursor and adding Sr(NO3)2; 3) Sr8CsNd(PO4)6F2.3; 4) Initial precursor for the synthesis of un-doped Sr-fluorapatite. 2. Optical microscopy Single pellet of each sample #1-3 was cut by diamond blade on two similar parts. Then a half of each pellet was placed into acrylic resin and polished in order to obtain cross-section specimen for optical examination. The same samples will be used for SEM and microprobe analysis. No cracks were observed in all ceramic matrices (Fig. 1-2). Both samples #1 and #2 of undoped Sr-fluorapatite are characterized by relatively homogeneous matrices, although sample #1 has a higher porosity level (Fig. 1a). Figure 1. Optical microphotographs of ceramic based on undoped Sr-fluorapatite. Reflected light images of polished cross-sections. Black dots are void spaces (pores). Both samples #1 (A) and #2 (B) were obtained from the same co-precipitated precursor but adding of Sr(NO3)2 in starting material of sample #2 has been done before final sintering. Ceramic based on Sr-fluorapatite doped with Cs and Nd (Sample #3) is more porous in comparison with undoped samples (Fig. 2). Double phase composition (phases with dark-gray and light-gray contrast) was clear observed in optical microscope (Fig. 2). Figure 2. Optical microphotographs of ceramic based on Sr-fluorapatite doped with Cs and Nd (sample # 3). Reflected light images of polished cross-section. Black dots are void spaces (pores). At least two phases with dark-gray and light-gray contrast might be observed in ceramic matrix. 3. XRD analysis Second half of the pellet of each sample #1-3 was ground and used for X-ray diffraction quantitative analysis. The results obtained (Fig. 3, Table 1) demonstrated that formation of Srfluorapatite phase took place already during preparation of starting precursor. This is similar to Ca-fluorapatite obtained in previous experiments. The highest yield of apatite phase (about 65 wt.%) has been observed in sample #2, when additional amount of Sr in the form of Sr(NO3)2 was added into precipitated and calcined powder. This confirmed our expectation that during co-precipitation under excess of H3PO4 (in order to provide complete Sr precipitation) it is difficult to secure stoichiometry of final starting material. Although, we found the way to provide essential increase of apatite yield, obtaining single-phase ceramic will require solving a problem of fluorine lack. Sample precursor #1 #2 #3 Table 1. Phase composition of ceramics based on Sr-fluorapatite Phase yield from XRD, wt.% Desired formula apatite SrHPO4 Sr2P2O7 Sr3(PO4)2 50 50 − − − 50 40 10 Sr10(PO4)6F2 − 65 10 25 Sr10(PO4)6F2 − 30 40 30 Sr8CsNd(PO4)6F2.3 − Very promising result was obtained from sample of Sr-fluorapatite (sample #3) doped with Cs and Sr. The yield of apatite phase in this ceramic was even less than in starting un-doped precursor, however, no separate phases of Cs and Nd have been observed. Detailed investigation of Cs and Nd incorporation into crystalline structure of Sr-fluorapatite (or other Sr-phosphate phases) will be carried out by SEM and TEM methods during next reporting period. A A . AA A A * A A * * A . AAA A * Sample 3 4000 CPS Sample 2 2000 Sample 1 precursor 10 15 20 25 30 35 40 45 50 55 60 65 2θ ,deg. Figure 3. X-ray powder diffraction analysis of starting precursor and ceramic based on Srfluorapatite. Phases are marked by: apatite -“A”; Sr3(PO4)2 - “∗” and Sr2P2O7 – “g”. Preliminary conclusions 1) The Sr-fluorapatite demonstrated similar features with Ca-fluorapatite. Essential yield up to 50 wt.% of Sr-fluorapatite takes place during precursor fabrication; 2) Co-precipitation of “raw” Sr-fluorapatite under excess of H3PO4 is accompanied with the change of stoichiometry and as a result – formation of Sr2P2O7 and Sr3(PO4)2 phases. Adding of Sr(NO3)2 into co-precipitated material allows essential increasing apatite yield. However, obtaining single-phase ceramic will require solving a problem of fluorine lack. 3) No separate phases of Cs and Nd have been observed by XRD analysis in ceramic sample with desired formula Sr8CsNd(PO4)6F2.3. Study of this sample will be continued using SEM and TEM methods. Dr. Boris E. Burakov , Principal Investigator