Effect of Ga Substitution on the Improper Ferroelectric Aluminate Sodalite‐Type Oxide Ca ₈ [AlO ₂ ] ₁₂ {WO ₄ } ₂

ABSTRACT This study examines the dielectric and elastic properties of aluminate sodalite‐type oxides Ca 8 [(Al 1− x Ga x )O 2 ] 12 {WO 4 } 2 ( x = 0.00, 0.05, and 0.10) to elucidate their complex phase‐transition behavior. Combined dielectric and elastic measurements reveal successive transitions from a paraelastic high‐temperature phase to a ferroelastic low‐temperature phase through intermediate ferroelastic phases. For x = 0.00, two intermediate phases emerge during cooling, whereas only one is observed upon heating, indicating an asymmetric transition pathway. Increasing Ga content progressively destabilizes and ultimately suppresses the intermediate phase, likely due to enhanced entropy effects. Broad dielectric and elastic anomalies observed below 500 K for x = 0.00 suggest the formation of polar nanoclusters, whose disappearance upon Ga substitution coincides with the loss of the intermediate phase. These findings have clarified composition–structure–property relationships in Ca 8 [(Al 1− x Ga x )O 2 ] 12 {WO 4 } 2 and provided insights into the design of functional properties in aluminate sodalite‐type oxides.