HW3_MS115a

HW3_MS115a - MS 115a Problem Set#3 assigned due 1 The ceramic compound SrTiO3 adopts the ideal perovskite structure and has a lattice constant of

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MS 115a, Problem Set #3 assigned 10/12/11 due 10/19/11 1. The ceramic compound SrTiO 3 adopts the ideal perovskite structure and has a lattice constant of 3.905 Å. Compute its density. 2. The compounds BaZrO 3 and LaAlO 3 also adopt the perovskite structure. Based on the ionic radii, predict whether these will be ideal cubic structures or will be distorted. Use the following ionic radii appropriate for the coordination environments: R (O 2- ) = 1.38 Å; R (Ba 2+ ) =1.61 Å; R (Zr 4+ ) = 0.72 Å; R (La 3+ ) = 1.36 Å; R (Al 3+ ) = 0.54 Å 3. The compounds ZrO 2 (zirconia) and CeO 2 (ceria) can take on the ideal fluorite structure. Calculate the expected coordination numbers for Zr and Ce (based on the radius ratios) and compare it with that for the cation in the ideal fluorite structure. Which of these two compounds is more stable in the ideal fluorite structure? R (O 2- ) = 1.38 Å R (Zr 4+ ) = 0.84 Å R (Ce 4+ ) = 1.14 Å 4. In fact, ZrO 2 exists in three forms. At very high temperatures (2400-2700
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This note was uploaded on 01/03/2012 for the course MS 115a taught by Professor List during the Fall '09 term at Caltech.

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HW3_MS115a - MS 115a Problem Set#3 assigned due 1 The ceramic compound SrTiO3 adopts the ideal perovskite structure and has a lattice constant of

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