Analysis of the Formation of Solid Solutions of REE Orthochromites

The dependence of unit cell parameters (UCPs) of LnCrO₃ (Ln = La–Lu, Y) orthochromites on effective ionic radii of Ln³⁺ cations is analyzed. It is shown that these dependences can be described by the following equations: \(a = {69}.{831}R_{\text{Ln}}^{3}-{223}.{91}R_{\text{Ln}}^{2}\text{+} {238}.{76}{{R}_{\text{Ln}}}-{79}.{162}\)  Å; b = 1.5893R_Ln + 5.9242 Å, c = 1.8469 R_Ln + 3.3691 Å, and V = 121.85R_Ln + 93.97 Å³, where R_Ln is the effective ionic radius of the Ln³⁺ cation with a confidence probability of 0.775, 0.989, 0.998, and 0.990, respectively. The obtained equations can be use in a priory calculations of the UCPs of isovalent solid substitution solutions of REE orthochromites (including high-entropy ones) using average effective radii of substituted Ln³⁺ cations. The tolerance factors of REE-, bismuth-, thallium-, and indium orthochromites are calculated. The possibility that an orthorhombic perovskite structure can be formed by the interaction of REE orthochromites with non-isostructural BiCrO₃ and ScCrO₃ chromites is considered.