This review provides a comprehensive evaluation of the state-of-knowledge of radiation effects in crystalline ceramics that may be used for the immobilization of high-level nuclear waste and plutonium. The current understanding of radiation damage processes, defect generation, microstructure development, theoretical methods, and experimental methods are reviewed. Fundamental scientific and technological issues that offer opportunities for research are identified. The most important issue is the need for an understanding of the radiation-induced structural changes at the atomic, microscopic, and macroscopic levels, and the effect of these changes on the release rates of radionuclides during corrosion.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/09D70E1FB1A625EC09BB98883C3A5ED3/S0884291400044411a.pdf/div-class-title-radiation-effects-in-crystalline-ceramics-for-the-immobilization-of-high-level-nuclear-waste-and-plutonium-div.pdf

Radiation effects in crystalline ceramics for the immobilization of high-level nuclear waste and plutonium

The vast majority of materials have a positive coefficient of thermal expansion and their volume increases on heating. There has been considerable recent interest in materials which display the unusual property of contracting in volume on heating; i.e. those with a negative coefficient of thermal expansion. This Perspective gives an overview of some of the physical phenomena that can give rise to this unusual effect. Recent insights into negative thermal expansion materials and some of their unusual structural properties are discussed.

Negative thermal expansion materials

There has been substantial renewed interest in negative thermal expansion following the discovery that cubic ZrW2O8 contracts over a temperature range in excess of 1000 K. Substances of many different kinds show negative thermal expansion, especially at low temperatures. In this article we review the underlying thermodynamics, emphasizing the roles of thermal stress and elasticity. We also discuss vibrational and non-vibrational mechanisms operating on the atomic scale that are responsible for negative expansion, both isotropic and anisotropic, in a wide range of materials.

https://iopscience.iop.org/article/10.1088/0953-8984/17/4/R03/pdf

Negative thermal expansion

Nasicons (sodium super ion conductors) are a class of solid electrolytes. Their structure, compositional diversity, evolution, and applications are reviewed. A wide range of materials is considered based on crystalline and glassy Nasicon compositions.

A wide-ranging review on Nasicon type materials

Review of crystalline lithium-ion conductors suitable for high temperature battery applications

The NaZr2(PO4)3 type structure (abbreviated as NZP or CTP, CaTi4(PO4)6), has emerged as a new family, which has extraordinary technological utility in three fields: fast-ion conductors, radwaste solidification and zero expansion ceramics. NZP or CTP is formed by an extraordinary range of discrete compositions and crystalline solutions. In this paper these compositions are classified according to their crystal chemical substitution scheme, and some uncommon trends in the systematic variation of their lattice parameters are shown. Some of the major trends are explained by correlation with the rotation of polyhedra in the structure.

Crystal chemistry of the NaZr2(PO4)3, NZP or CTP, structure family

[CTP]: A new structural family of near-zero expansion ceramics

[NZP], a new radiophase for ceramic nuclear waste forms

Compositions in the series Na1+xZr2P3-xSixO12 and Na1+4zZr2-zP3O12, where x = 0≤x≤1 and z=0≤z≤1/2, have thermal expansions that can be controlled (by selecting the composition) to values in the range <10×10-7 in a temperature regime of a few hundred degrees. The lowest a values were obtained for x ∼0.33 and z∼0.125.

Ultralow-expansion ceramics in the system na2o-zro2p2o5-sio2

A structural model is proposed to describe the highly anisotropic thermal expansion in the sodium zirconium phosphate NaZr2P3O12 structure as a result of the thermal motion of the polyhedra in the structure. In the proposed model the rotations of the phosphate tetrahedra are coupled to the rotation of the zirconium octahedra. Of the two versions considered, the first one allows angular distortions to occur only in the ZrO6 octahedra; the second one permits all polyhedra to be distorted.

J. Alamo

Papers

Crystal chemistry of the NaZr2(PO4)3, NZP or CTP, structure family

[CTP]: A new structural family of near-zero expansion ceramics

[NZP], a new radiophase for ceramic nuclear waste forms

Ultralow-expansion ceramics in the system na2o-zro2p2o5-sio2

Structural model for thermal expansion in MZr2P3O12 (M=Li, Na, K, Rb, Cs)