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Data are reported for the linear thermal expansivity, alpha , of one sample of La1.85Sr0.15CuO4 and four samples of YBa2Cu3O7 in the temperature range 2 to 1000 K. Values are calculated for the Gruneisen parameter, gamma approximately=0.7, using ultrasonic data for the elastic moduli. Published compressibility measurements give much higher values of the bulk modulus and of gamma .

The Tl-Ba-Ca-Cu-O system, when prepared by standard sintering procedures, shows mass loss by volatilisation of Tl even at sintering temperatures lower than the decomposition temperature of Tl2O3 (850°C). The disappearance of Tl results in difficulties in preparation, especially since Tl2O3 emission is severely toxic. The use of a two-stage sintering technique involves first the preparation of Ba-Ca-Cu-O by standard ceramic processing, so that TI2O3 can be added to the sintered Ba-Ca-Cu-0, enclosed in a silver tube, and sintered. This technique ensures reproducible results and safety. Two superconducting phases were confirmed by Tc measurements, x-ray diffraction patterns, and electron microanalysis. The materials were characterised by DTA, electrical and magnetic measurement, and TEM. Prolonged sintering degraded the superconducting properties, probably due to thallium evolution. Transition broadening in applied magnetic fields is ascribed to anisotropy.

Measurements of thermal expansion through the Neel transition show that, when V, Mo or Mn atoms are substituted in the Cr lattice, the nature of the antiferromagnetic transition changes from weak first order in pure Cr to continuous. The possible tricritical point in CrV is close to 0.2 at.% V.

The linear thermal expansions of CaF2, BaF2, SrF2, PbF2 and SrCl2 have been measured from room temperature up to their melting points. The linear coefficient alpha exhibits a Schottky-like bump similar to that observed previously for the heat capacity, Cp, and associated with fast-ion conduction in these fluorite-structure materials. Values for the Gruneisen parameter gamma (T) are included.

Measurements of the coefficient of linear thermal expansion of pure polycrystalline silicon were made with a polarization interferometer and a platinum resistance thermometer with an estimated error of less than 0.01 × 10-6 K-1.

The linear thermal expansion coefficient alpha of pure Cr and of dilute CrV alloys containing up to 5 at.% V has been measured from 2 to 700K. Paramagnetic Cr95V5 provides a reference to determine the effect of antiferromagnetic ordering in the other samples, whose Neel temperatures TN range from 27K for Cr+3.4 at.% V to 311K for Cr. In each case alpha (T) falls well below the paramagnetic value but returns to the paramagnetic alpha p(T) curve at a temperature somewhat above TN. Below about 20K all the antiferromagnets have large negative alpha linear in T. Beyond about 500K the Gruneisen parameter gamma of Cr is about 1.5, and it remains roughly constant up to 1500K.

An instrument for measuring the absolute thermal expansion of solids up to 1000 degrees C is described. A sensitivity of 10-8 degrees C-1 was achieved by means of a frequency stabilizer laser and a polarization interferometer. Details of the laser stabilization technique interferometer, automatic polarimeter, sample chamber and preliminary results on tungsten are given.