Thanks, PP.
Claire, there's nothing wrong with supplementing your portfolio with inflation-protected bonds, but they're not a replacement for regular bonds because they often move in different directions.
More info here. I should say when working with a smaller portfolio (let's say under $50K), you really can't do complete diversification. One reason for this is the inability to meet funds' minimum balances. For smaller portfolios, I prefer a lifecycle fund such as Vanguard Retirement 2045 with maybe a piece of real estate or emerging markets added in.