Epr of Fe3+ and Cr3+ Ions in NZP Ceramics

1999 ◽  
Vol 556 ◽  
Author(s):  
A. Y. Troole ◽  
S. V. Stefanovsky ◽  
L. D. Bogomolova
Keyword(s):  
Thermodynamic Stability ◽  
Zirconium Phosphate ◽  
Coordination Polyhedra ◽  
Sodium Zirconium ◽  
Distortion Analysis ◽  
The Stability ◽  
Nzp Ceramics ◽  
Nzp Structure ◽  
Sodium Zirconium Phosphate

AbstractA new method to estimate the thermodynamic stability of crystalline host phases for radwaste is based on the determination of the degree of coordination polyhedra distortion. Analysis of the stability of sodium zirconium phosphate (NZP) structure containing Fe and Cr has been completed. The NZP structure can incorporate a limited amount of iron (∼2 mol. % Fe2o3). From the EPR study, Fe3+ and Cr3+ ions occupy two different structural positions substituting for Zr4+and Na+. Moreover, these ions can enter extra phases.

GEL Adsorption Processing for Waste Solidification in 'NZP' Ceramics

1983 ◽  
Vol 26 ◽  
Author(s):  
L.J. Yang ◽  
S. Komarneni ◽  
R. Roy
Keyword(s):  
Zirconium Phosphate ◽  
Adsorption Process ◽  
Hydrothermal Conditions ◽  
Waste Solution ◽  
Waste Forms ◽  
Sodium Zirconium ◽  
Reducing Conditions ◽  
Adsorption Processing ◽  
Nzp Ceramics ◽  
Sodium Zirconium Phosphate

ABSTRACTSimulated PW-4b waste solution along with Na additive was mixed with Zr-P-O gel, dried and then fired to form the desired sodium zirconium phosphate, NaZr2 (PO4) 3 [NZP] ceramic. NZP and monazite were the only phases produced upon firing at 900°C with 10 to 40% of PW-4b mixed with the gel. CsZr2(PO4) 3 which is isostructural with NZP was also identified when fired under reducing conditions. The -200 mesh powders of these waste forms prepared under reducing conditions showed excellent leach resistance under hydrothermal conditions.Alternatively, PW-4b and Three Mile Island (TMI) wastes were adsorbed on Zr-P-O gel in a column. The gel was dried, pelletized and fired to form the desired [NZP] ceramic. Cesium was found to be selective on the Zr-P-O gel because no breakthrough of Cs was detected up to 38 column volumes of TMI waste. Thus, it is possible to use a tailored gel to sorb Cs and/or Sr from accident waste water and then fired the bed to form the [NZP] ceramic below 1000°C. The main advantages of the gel adsorption process are its simplicity and its enormous compositional flexibility.

High-temperature crystal chemistry of sodium zirconium phosphate (NZP)

1987 ◽  
Vol 2 (3) ◽  
pp. 329-337 ◽  
Author(s):  
R. M. Hazen ◽  
L. W. Finger ◽  
D. K. Agrawal ◽  
H. A. McKinstry ◽  
Anthony J. Perrotta
Keyword(s):  
Thermal Expansion ◽  
High Temperature ◽  
Zirconium Phosphate ◽  
Structural Model ◽  
Average Volume ◽  
Coordination Polyhedra ◽  
X Ray ◽  
Sodium Zirconium ◽  
Cation Coordination ◽  
Sodium Zirconium Phosphate

High-temperature crystal structures of NZP (Na1+xZr2P3−xSixO12) have been determined by x-ray measurements made on single crystals. Thermal expansion of NZP (x = 0.11) parallel to the hexagonal c axis is positive (about 22.4 ⊠ 10−6°C−1 between 25° and 700°C), whereas expansion perpendicular to c is slightly negative (about 5.4 ⊠ 10−6°C−1), resulting in an average volume thermal expansion of 11.8 ⊠ 10−6°C−1. A proposed structural model to interpret this anisotropic thermal expansion of NZP is tested to prove the model's validity. In this model the rotation of the phosphate tetrahedron is coupled to the rotation of the zirconium octahedron. The observed thermal expansions of sodium, zirconium, and phosphorus cation coordination polyhedra are 10.8, 0.00, and −0.23 (all × 10−6°C−1), respectively. The large thermal expansion of the sodium site is offset by rotations in the Zr–P polyhedral framework, thus yielding the low net expansion of NZP.

Comparison of sodium zirconium phosphate and calcium zirconium phosphate structures for the retention of fluoride

2013 ◽  
Vol 299 (1) ◽  
pp. 19-24 ◽  
Author(s):  
Ambarish Dey ◽  
Amit Das Gupta ◽  
Debrata Basu ◽  
Ritu D. Ambashta ◽  
P. K. Wattal ◽  
...  
Keyword(s):  
Zirconium Phosphate ◽  
Sodium Zirconium ◽  
Sodium Zirconium Phosphate

Relationship Between Thermal Expansion and Crystal Chemical Parameters in Diborides

1986 ◽  
Vol 30 ◽  
pp. 503-510
Author(s):  
H.A. McKinstry ◽  
Lai Daik Chai ◽  
R.V. Sara ◽  
K.E. Spear
Keyword(s):  
Thermal Expansion ◽  
High Temperature ◽  
Zirconium Phosphate ◽  
Hexagonal Structure ◽  
Crystal Chemical ◽  
X Ray Diffraction ◽  
Chemical Parameters ◽  
X Ray ◽  
Sodium Zirconium ◽  
Sodium Zirconium Phosphate

Thermal expansion is an interesting, ubiquitous and neglected property of materials. Recently, Lenain et al. (1985) and Limaye (1986) have been investigating anisotropy in the low-expansion structures of the sodium zirconium phosphate family. In the hexagonal structure one axis expands while another contracts. In going from the calcium to the strontium analog the anisotropy actually changes sign. A change in anisotropy between CrB2 and TiB2 had been observed by R.V. Sara (1960). The results in Fig. 1 obtained by high temperature x-ray diffraction measurements indicate that for TiB2 the thermal expansion of the c-axis is greater than the expansion of the a-axis, whereas for CrB2 the reverse is true.

Crystallographic evaluation of sodium zirconium phosphate as a host structure for immobilization of cesium

2010 ◽  
Vol 45 (2) ◽  
pp. 533-545 ◽  
Author(s):  
Rashmi Chourasia ◽  
Ashish Bohre ◽  
Ritu D. Ambastha ◽  
O. P. Shrivastava ◽  
P. K. Wattal
Keyword(s):  
Zirconium Phosphate ◽  
Sodium Zirconium ◽  
Host Structure ◽  
Sodium Zirconium Phosphate
Sign in / Sign up

Export Citation Format

Share Document