Aqueous sol-gel processing was used to synthesize neodymium-doped magnesium hexaaluminate (La1-xNdxMgAl11O19; x = 0, 0.3, 0.4, 0.5) ceramic powder and subsequently calcined at 1450 and 1600 degrees C for 2 h. Randomly grown platelets of lanthanum-magnesium hexaaluminate formed a porous interlocking structure. Presence of various percentages of neodymium oxide significantly modifies the porous interlocking microstructure into self-reinforced, card-house-like microstructure. Platelets of rare earth-rich magnesium hexaaluminate were grown preferentially more than the stoichiometric rare earth magnesium hexaaluminate at elevated temperature greater than 1450 degrees C. Rare earth-rich magnesium hexaaluminate platelets form the skeleton of a card-house structure and the tiny platelets of stoichiometric rare earth magnesium hexaaluminate fill the house. The specific heat capacities, micro-hardness, and fracture toughness were studied in details.