How did the Congress of Vienna create the Bourbon Duchy of Lucca?

The Congress of Vienna created the Bourbon Duchy of Lucca in 1815 as a compensatory measure for the house of Bourbon-Parma.1

Following the Napoleonic Wars, the Congress assigned the Duchy of Parma to Marie-Louise, the estranged consort of Napoleon, for her lifetime. Because this arrangement left the Bourbon-Parma family dispossessed of their traditional lands, the Congress established the Duchy of Lucca as an alternative territory for them. The duchy was granted to the Spanish infanta María Luisa, the widow of the former king of Etruria, and later passed to her son, Charles Louis.123

This arrangement was intended to be temporary; under the Treaty of Paris of 1817, it was prescribed that Parma would revert to the Bourbons upon the death of Marie-Louise. Consequently, the Bourbons renounced Lucca to the Habsburgs of Tuscany in 1847, shortly before they succeeded to the Duchy of Parma.1