Ion-beam irradiation of Gd₂Sn₂O₇ and Gd₂Hf₂O₇ pyrochlore: Bond-type effect

Abstract

Ceramics with III-IV pyrochlore compositions, A3+2B4+2O7 (A = Y and rare earth elements; B = Ti, Zr, Sn, or Hf), show a wide range of responses to ion-beam irradiation. To evaluate the role of the B-site cations on the radiation stability ofthe pyrochlore structure-type, Gd2Sn2O7 and Gd2Hf2O7 have been irradiated by1 MeV Kr+. The results are discussed in terms of the ionic size and type ofbonding of Sn4+ and Hf4+ and compared to previous results for titanate andzirconate pyrochlores. Gd2Sn2O7 is sensitive to ion beam–induced amorphizationwith a critical amorphization dose of approximately 3.4 displacements per atom(dpa) (2.62 × 1015 ions/cm2) at room temperature and a critical amorphization temperature of approximately 350 K. Gd2Hf2O7 does not become amorphous at adose of approximately 4.54 displacement per [lattice] atom (3.13 × 1015 ions/cm2) at room temperature, but instead is transformed to a disordered fluorite structure upon ion-beam irradiation. Although the radius ratio of the A- to B-site cations provides a general indication of the type of radiation response of different pyrochlore compositions, the results for Gd2Sn2O7 emphasize the importance of bond type, particularly the covalency of the 〈Sn–O〉 bond in determining the radiation response.

Response of Gd2Ti2O7 and La2Ti2O7 to swift-heavy ion irradiation and annealing

“…In order to understand compositional and structural influences on radiation effects, extensive ion-beam irradiation studies using various ion species and energies have been completed on a wide variety of A 2 B 2 O 7 compositions [9][10][11][12][13][14][15][16][17]. Irradiation experiments with swift heavy ions of initial energies in the range of MeV to GeV, which deposit energy into a material mainly through electronic excitation and are useful for simulating the effects of nuclear fission fragment irradiation, were mainly performed on titanate and zirconate pyrochlores [9][10][11][12]. These studies emphasize that the radiation tolerance of pyrochlores is proportional to r A /r B , and that tolerant materials show disordering to a fluorite structure rather than amorphizing under irradiation.…”

Structure and performance evolution of the system (Gd1−Nd )2(Zr1−Ce )2O7 (0 ≤x, y≤ 1.0)

“…Cations with similar radius and equal valence could be incorporated into A/B sites [10,11], which has promoted the potential application of pyrochlore, and has accelerated large amounts of researches in radioactive elements immobilization [12,13]. For example, the solubility of Nd 3+ is investigated to simulate the incorporation of Am 3+ at the A site, and Ce 4+ is incorporated at the B site to simulate the solubility of Pu 4+ in Gd 2 Zr 2 O 7 [14][15][16]. While recently Gregg et al has shown that Pu can be exchanged for both the A and B site within lanthanum zirconate pyrochlore [17].…”

Preparation and high temperature-XRD studies on a pyrochlore series with the general composition Gd2−xNdxZr2O7

“…They have studied the thermal expansion coefficients of partially and completely substituted La 2 Zr 2 O 7 , with substitution at La site by other trivalent rare-earths as Nd 3+ , Eu 3+ and Gd 3+ . Lian et al [19] investigated the effect of ion beam irradiation on pyrochlores with general composition A 2 3+ B 2 4+ O 7 (A = Y and rare-earth elements; B = Ti, Zr, Sn, or Hf). Their study revealed that the radius ratio (r A /r B ) has got a strong bearing on stability of pyrochlores against the ion beam irradiation.…”