Temperature dependence of the elastic constants of single-crystal rutile between 4° and 583°K*

Abstract Measurements of all the six principal elastic constants of single-crystal rutile were made in the temperature range of 298–583°K. The temperature derivatives (in kb/deg) at 298°K are: dC11/dT = − 0·510, dC33/dT = − 0·900, dC44/dT = − 0·220, dC66dT = − 0·458, dC12/dT = − 0·580, and dC13/dT = − 0·330. Measurements of the four modes, C11, C′ = (C11 — C12)/2, C66, and C110L = (C11 + C12 + 2C66)/2, were extended to 4°K. Two features related to the temperature and volume dependences of the lattice vibrational frequencies are revealed: first, all the measured dClj/dT except dC′/dT become less negative with increasing temperature above 100°K. Second, dC′/dT is positive at all temperatures but decreases with increasing temperature at temperatures > 300°K. Indirectly shown is that (∂C′/∂P)T having a value of − 1·32 at 298°K, decreases with decreasing temperatures. The significance of this latter fact is discussed in light of the computation of Gruneisen mode γ's from the acoustic (∂Cij/∂P)T values, and the results are compared with the γ (αv) values obtained by Kirby from thermal expansion data. It is concluded that the large increase in γ(αv) at low temperatures cannot be ascribed to a large temperature dependence of (∂C′/∂P)T. Therefore, Kirby's explanation, that the large increase in γ(αv) is caused by the large volume dependence of the acoustical mode frequencies, is not substantiated.